Method for selecting a resin substrate for a gas barrier film and a resin substrate for a gas barrier film

Abstract

To provide a selection method of a resin base material for a gas barrier film to be used for a gas barrier film exhibiting excellent gas barrier properties while having sufficient adhesion strength as a wrapping material.SOLUTION: A selection method of a resin base material for a gas barrier film includes the steps of: measuring a black area ratio on a surface of a resin base material raw fabric with a measuring method below to prepare a resin base material raw fabric with a black area ratio of 0.15% or less at least on one side thereof as a resin base material. <The measuring method> includes: imaging an arbitrary area of 1281 square μm on one side of a resin base material with an optical microscope to obtain a photographic image of 1024×1024 pixel; converting the photographic image into a monochrome image of 256 levels; setting, as a threshold value, a value obtained by subtracting 30 from a most frequent value of luminance in the monochrome image using an image analyzing software; binarizing the luminance with a value lower than the threshold value being black and a value equal to or higher than the threshold value being white; and setting a ratio of a total area of the black area of size 100 μm2 or larger in the 1281 square μm as a black area ratio.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for selecting a resin substrate for a gas barrier film and a resin substrate for a gas barrier film. [Background technology]

[0002] Packaging materials used for packaging foods, pharmaceuticals, etc. are required to have gas barrier properties, i.e., the ability to prevent the intrusion of gases (water vapor, oxygen, etc.) that denature the contents, in order to prevent deterioration and spoilage of the contents and maintain their functionality and quality. For this reason, film materials with gas barrier properties (gas barrier films) are used for these packaging materials.

[0003] Known gas barrier films include those in which a gas barrier layer made of a material having gas barrier properties is provided on the surface of a resin substrate. Known gas barrier layers include metal foils, metal vapor deposition films, and films formed by wet coating. Known films that exhibit oxygen barrier properties include resin films formed from coating agents containing water-soluble polymers, resins such as polyvinylidene chloride, and inorganic layered mineral composite resin films formed from coating agents containing water-soluble polymers and inorganic layered minerals (Patent Document 1). Other proposed gas barrier layers include a gas barrier layer formed by sequentially laminating a vapor-deposited thin film layer made of an inorganic oxide and a gas barrier composite coating containing a water-soluble polymer, an inorganic layered compound, and a metal alkoxide (Patent Document 2), and a gas barrier layer containing a polyvalent metal salt of a carboxylic acid, which is a reaction product of a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound (Patent Document 3).

[0004] In order to improve gas barrier properties, for example, Patent Document 4 proposes a gas barrier film in which a coating is formed on at least one surface of a substrate, and the surface of the coating has a surface roughness parameter Rt / Ra of 20 or less. Here, Rt is the distance between the maximum peak and the deepest valley on the surface roughness curve, and Ra is the centerline average roughness. The gas barrier film of Patent Document 4 aims to improve gas barrier properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6191221 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-254994 [Patent Document 3] Patent No. 4373797 [Patent Document 4] Japanese Patent Application Publication No. 9-150484 Summary of the Invention [Problem to be solved by the invention]

[0006] However, gas barrier films in which a coating is formed on the surface of a resin substrate by a wet coating method, a vapor deposition method, or a sputtering method sometimes have unstable oxygen barrier properties depending on the production lot. Specifically, the oxygen barrier properties of the gas barrier film are sometimes inferior to the original oxygen barrier properties, i.e., the oxygen barrier properties expected from the material constituting the coating and the thickness of the coating. In particular, such problems tend to occur more easily when the coating thickness is thin. Therefore, it is necessary to address this by making the gas barrier layer thicker than necessary, which has led to problems of poor productivity and excessive material costs.

[0007] Furthermore, the surface of the gas barrier film may be printed, and therefore the gas barrier film is required to have a surface that is easy to print on (printability).

[0008] The present disclosure has been made in view of the above circumstances, and aims to provide a method for selecting a resin substrate for a gas barrier film, and a resin substrate for a gas barrier film, which is used in a gas barrier film that exhibits excellent gas barrier properties by fully exhibiting the inherent oxygen barrier properties even when the thickness of a coating for imparting oxygen barrier properties is thin, and has good printability. [Means for solving the problem]

[0009] The method for selecting a resin substrate for a gas barrier film according to the present invention comprises the steps of measuring the black area ratio of a surface of a raw resin substrate sheet by the following measurement method, and preparing a raw resin substrate sheet having a black area ratio of 0.15% or less on at least one side as the resin substrate. <Measurement method> An arbitrary 1281 μm square area on one side of the resin substrate was photographed with an optical microscope to obtain a 1024 × 1024 pixel photograph. The photographed image was converted into a monochrome image with 256 gradations using image analysis software. The threshold value was determined by subtracting 30 from the most frequent brightness value in the monochrome image. Brightness was binarized with values ​​below the threshold as black and values ​​above the threshold as white. A 100 μm square area of ​​1281 μm square was then measured. 2 The ratio of the total area of ​​black areas of the above size is defined as the black area ratio.

[0010] The resin substrate for a gas barrier film according to the present invention is selected by the above-mentioned selection method. [Effects of the Invention]

[0011] The present invention can provide a method for selecting a resin substrate for a gas barrier film to be used in a gas barrier film that exhibits excellent gas barrier properties by fully exhibiting the inherent oxygen barrier properties even when the thickness of a coating for imparting oxygen barrier properties is thin, and that has sufficient adhesive strength for use as a packaging material, and a resin substrate for a gas barrier film. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view of the gas barrier film of the first embodiment. [Figure 2] FIG. 2 is an image of one surface of the resin substrate of the first embodiment photographed with an optical microscope. [Figure 3] FIG. 3 is an example of a histogram used to calculate the black area ratio. [Figure 4] FIG. 4 is a cross-sectional view of the gas barrier film of the second embodiment. [Figure 5] FIG. 5 is a schematic diagram illustrating a measuring device for measuring the number of protrusions on the first surface of the resin substrate. [Figure 6] FIG. 6 is a schematic diagram illustrating the principle of detecting a protrusion. [Figure 7] FIG. 7 shows a photographed image of the first surface of the resin substrate of the example, and an analysis image showing protrusions detected from the photographed image. [Figure 8] Figure 8 is a cross-sectional electron microscope image taken with a focused ion / electron beam processing and observation device, showing the occurrence of film defects in the area where the AB agent is present on the resin substrate. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Embodiment 1) To investigate the cause of the above-mentioned problem, the inventors conducted detailed observations of the surface and cross section of a gas barrier film with poor oxygen barrier properties using optical and electron microscopes. Cross-sectional electron microscope observations were performed using a focused ion / electron beam processing and observation device at locations where an antiblocking agent (hereinafter also referred to as "AB agent"), which is added to prevent blocking of the resin substrate, was present. As a result, it was confirmed that defects several micrometers in width had occurred in the film at locations where the AB agent protruded. It is believed that these defects acted as paths for gas permeation, preventing sufficient oxygen barrier properties from being exhibited.

[0014] The surface of the resin substrate has protrusions of various sizes caused by the AB agent. The height and density of the protrusions of the AB agent vary depending on the production lot of the resin substrate. When the surface of the resin substrate was coated with a gas barrier film, the film did not form locally at the locations of the large protrusions, resulting in defects and unstable oxygen barrier properties.

[0015] Furthermore, by observing in detail with a microscope the transfer failure of fine dots (sometimes called missing dots) that occurs in the highlight printed areas of the gas barrier film, it was confirmed that missing dots are more likely to occur in areas where the AB agent protrudes highly.

[0016] Therefore, the present inventors have devised a method for quickly and accurately grasping the surface condition of a wide range of a resin substrate, which affects the oxygen barrier property and printability of a gas barrier film, and have performed binarization processing on an optical microscope image of the surface of the resin substrate to obtain a 100 μm 2 It was discovered that when the total area ratio of the black regions (hereinafter referred to as the black area ratio) is 0.15% or less, the oxygen barrier performance is excellent and the printability on the gas barrier film is good, which led to the present disclosure.

[0017] The gas barrier film of the present disclosure will be described with reference to an embodiment.

[0018] Fig. 1 is a schematic cross-sectional view of a gas barrier film 1 according to embodiment 1. For the sake of convenience, the dimensional ratios in Fig. 1 are different from the actual ratios.

[0019] The gas barrier film 1 has a resin substrate 10, an underlayer 30, an inorganic oxide layer 40, and an oxygen barrier coating 20. Note that either the underlayer 30 or the inorganic oxide layer 40 may be omitted.

[0020] The underlayer 30 is laminated in contact with one surface 12 of the resin substrate 10, and an inorganic oxide layer 40 is laminated on the surface of the underlayer 30 opposite the surface in contact with the resin substrate 10. The inorganic oxide layer 40 is laminated in contact with the underlayer 30, and the oxygen barrier coating 20 is located in contact with the surface of the inorganic oxide layer 40 opposite the surface in contact with the underlayer 30. If the underlayer 30 is not provided, the inorganic oxide layer 40 is laminated on one surface 12 of the resin substrate 10. If the inorganic oxide layer 40 is not provided, the oxygen barrier coating 20 is laminated on the underlayer 30.

[0021] <Resin substrate> The resin substrate 10 includes a resin. Examples of resins constituting the resin substrate 10 include olefin-based resins such as polyethylene, polypropylene, polymers of olefins having 2 to 10 carbon atoms, and propylene-ethylene copolymers; polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamide-based resins such as aliphatic polyamides such as nylon 6 and nylon 66, and aromatic polyamides such as polymetaxylylene adipamide; vinyl-based resins such as polystyrene, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, and ethylene-vinyl alcohol copolymer; acrylic-based resins such as homopolymers or copolymers of (meth)acrylic monomers such as polymethyl methacrylate and polyacrylonitrile; cellophane; and engineering plastics such as polycarbonate and polyimide. These resins may be used alone or in combination of two or more.

[0022] Examples of the resin substrate 10 include a single-layer film made of a single resin, and a single-layer or laminated film made of multiple resins. A laminated substrate in which the above-mentioned resin is laminated on another substrate (metal, wood, paper, ceramics, etc.) may also be used. The resin substrate 10 may be a single layer or two or more layers. Preferred examples of the resin substrate 10 include polyolefin-based resin films (particularly polyethylene films, polypropylene films, etc.), polyester-based resin films (particularly polyethylene terephthalate-based resin films), and polyamide-based resin films (particularly nylon films).

[0023] The resin substrate 10 may be an unstretched film or a uniaxially or biaxially stretched film. From the viewpoint of excellent water vapor barrier properties, polyethylene film or polypropylene film is preferred as the resin substrate 10, and biaxially stretched polypropylene film (OPP) is particularly preferred. The OPP may be a film formed from at least one polymer selected from homopolymers, random copolymers, and block copolymers. A homopolymer is a polypropylene consisting solely of propylene. A random copolymer is a polypropylene in which the main monomer propylene and a small amount of a comonomer other than propylene are randomly copolymerized to form a homogeneous phase. A block copolymer is a polypropylene in which the main monomer propylene and the comonomer are copolymerized in a block manner or polymerized into a rubber-like form to form a heterogeneous phase. When the resin substrate 10 is OPP, the OPP may be a single layer or two or more layers.

[0024] One surface 12 of the resin substrate 10 may be subjected to a surface treatment such as chemical treatment, solvent treatment, corona treatment, low-temperature plasma treatment, or ozone treatment in order to improve adhesion to the underlayer 30 or the inorganic oxide layer 40.

[0025] The resin substrate 10 may contain additives such as fillers, antiblocking agents, antistatic agents, plasticizers, lubricants, antioxidants, etc. These additives may be used alone or in combination of two or more.

[0026] When the resin substrate 10 contains an antiblocking agent (hereinafter also referred to as "AB agent"), unevenness resulting from the AB agent is formed on one surface 12 of the resin substrate 10. By containing the AB agent, the resin substrate 10 imparts convexities to the surface of the resin substrate 10, thereby suppressing the occurrence of blocking in the film. That is, by containing the AB agent in the resin substrate 10, the blocking resistance of the film is increased. This makes it easier to wind up the film, and improves the processing characteristics of the film. Therefore, it is preferable that the resin substrate 10 contains an AB agent. On the other hand, if large convexities are formed on one surface 12 of the resin substrate 10, defects that serve as gas permeation paths are likely to occur in the undercoat layer 30, inorganic oxide layer 40, and oxygen barrier coating 20 formed thereon. This raises the risk of a decrease in the oxygen barrier properties of the gas barrier film 1.

[0027] When the resin substrate 10 contains an AB agent, the AB agent is dispersed in the resin substrate 10. A plurality of protrusions derived from the AB agent are locally present on one surface 12 or the other surface 14 of the resin substrate 10. On one surface 12 and the other surface 14, the AB agent may be exposed or may be covered with resin.

[0028] The AB agent is a solid particle, and examples thereof include organic particles and inorganic particles. Examples of organic particles include polymethyl methacrylate particles, polystyrene particles, and polyamide particles. These organic particles are obtained, for example, by emulsion polymerization or suspension polymerization. Examples of inorganic particles include silica particles, zeolite, talc, kaolinite, and feldspar. These AB agents may be used alone or in combination of two or more.

[0029] The average particle size of the AB agent is preferably 0.1 to 5 μm, for example, in consideration of the appearance, transparency, possibility of the AB agent falling off, and anti-blocking performance of the gas barrier film 1. The average particle size of the AB agent is the weight average diameter measured by the Coulter method.

[0030] When the resin substrate 10 contains an AB agent, the content of the AB agent is preferably, for example, 0.05 to 0.5 parts by mass relative to 100 parts by mass of the resin constituting the resin substrate 10. When the content of the AB agent is equal to or greater than the above lower limit, it is easy to improve the processing characteristics of the film that is the raw material for the resin substrate 10. When the content of the AB agent is equal to or less than the above upper limit, it is easy to prevent a decrease in the oxygen barrier property of the gas barrier film 1.

[0031] The black area ratio of one surface 12 of the resin substrate 10 is 0.15% or less, more preferably 0.12% or less, and even more preferably 0.10% or less. When the black area ratio is equal to or less than the above upper limit, the oxygen barrier properties of the gas barrier film 1 are more likely to be improved. In addition, when the black area ratio is equal to or less than the above upper limit, the printability of the gas barrier film 1, particularly when using a polypropylene film or a polyethylene terephthalate resin film, is more likely to be improved. The lower limit of the black area ratio is not particularly limited, and is 0% or more.

[0032] Here, "improving printability" means suppressing ink loss (sometimes called "missing dots") in highlight areas (printed areas with low dot area ratios) when gravure printing is performed on the oxygen barrier coating 20 of the gas barrier film. The black area ratio can be adjusted, for example, by the material, average particle size and content of the AB agent contained in the resin substrate 10, the properties of the resin forming one surface 12 of the resin substrate 10, the film manufacturing conditions, etc.

[0033] When the brightness of the surface of the resin substrate 10 is binarized and the black spots (black dots) are observed under an electron microscope, protrusions are found. The larger the black dots, the higher the height of the protrusions. 2 In areas where black dots (protrusions) of this size or larger are present, coating defects in the oxygen barrier coating and ink loss during printing are likely to occur. In other words, the smaller the black area ratio, the fewer protrusions that adversely affect the oxygen barrier property and printability on one side 12 of the resin substrate 10, and the more improved the oxygen barrier property of the gas barrier film 1 and the better the printability.

[0034] The black area ratio in this specification can be measured by the following measurement method. <Measurement method> An arbitrary area of ​​1281 μm square on one surface 12 of the resin substrate 10 is photographed with an optical microscope to obtain a photographed image of 1024×1024 pixels. An example of the photographed image is shown in FIG.

[0035] FIG. 2 is an image of one surface 12 of the resin substrate 10 photographed with an optical microscope. In FIG. 2, 100 represents a flat portion, and 110 represents a protrusion. Examples of the protrusion 110 include foreign matter, an AB agent, and residual resin. As shown in FIG. 2, the flat portion 100 appears gray, and the protrusion 110 appears black. The brightness of the flat portion 100 corresponds to the mode of brightness, which will be described later.

[0036] Next, using image analysis software, the acquired 1024 x 1024 pixel captured image is converted into a 256-level monochrome image. The brightness distribution in the converted monochrome image is plotted to create a histogram. An example of a histogram is shown in Figure 3.

[0037] In FIG. 3, the horizontal axis represents the luminance converted into a monochrome image with 256 gradations. The luminance in a monochrome image is an integer between 0 and 255. The vertical axis represents the frequency of luminance. In FIG. 3, the minimum luminance value is 26 and the maximum luminance value is 255. The most frequent luminance value is the luminance value that is most frequently distributed in a monochrome image. P in FIG. 3 represents the most frequent luminance value. In FIG. 3, P=160.

[0038] Next, the brightness of the monochrome image is binarized by setting a threshold value obtained by subtracting 30 from the most frequent brightness value, and setting values ​​below the threshold to black and values ​​above the threshold to white. In the monochrome image of FIG. 3, the threshold value that marks the boundary between black and white is the most frequent brightness value subtracted by 30 (P-30). In FIG. 3, the threshold is 130. That is, in FIG. 3, the binarization process is performed by setting brightness values ​​below 130 to "black" and brightness values ​​above 130 to "white."

[0039] From the viewpoint of improving the accuracy of the black area ratio value, it is preferable that the brightness histogram of the acquired image has a sharp shape. Here, a "sharp shape" can be determined, for example, by the width W of the histogram at half the height (H / 2) of the peak height H at the mode P of the histogram (hereinafter also referred to as "half-width"). The half-width W is, for example, preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. When the half-width W is equal to or less than the above upper limit, the histogram has a sharp shape, and the accuracy of the black area ratio value can be improved. The lower limit of the half-width W is not particularly limited, but is substantially 2 or more.

[0040] From the binarized 1281 × 1281 μm (1024 × 1024 pixel) image, 2 The black area ratio is the percentage of the total area of ​​black areas of the above size. The black area ratio is the arithmetic average of the values ​​obtained in any three areas.

[0041] As the optical microscope, the optical microscope "OLS-4000" manufactured by Olympus Corporation is preferred. As the image analysis software, "Scion ImageJ" manufactured by Scion Corporation is preferred. stomach.

[0042] The image acquisition conditions will be described. (Image acquisition conditions) The resin substrate 10 for which the black area ratio is to be determined is attached to a glass slide using black double-sided film tape (Teraoka Seisakusho, 7694) with the coating agent side (one side 12) facing up. Using an optical microscope (Olympus, OLS-4000) and a 10x objective lens (MPFLN10), images of a 1281 μm x 1281 μm area are captured as 1024 x 1024 pixel images from three random locations on the resin substrate 10 on the glass slide. The light intensity used for image capture is optional, but it is preferable to adjust the light intensity so that the most frequent image brightness is in the range of 80 to 200 in 256 gradations.

[0043] The image analysis conditions are as follows: (Image analysis conditions) - Discard color information: 8bit. ·Binarization threshold: The value obtained by subtracting 30 from the most frequent luminance value. Scale setting: Set Scale Distance in pixel: 1024, Known distance: 1281, Unit of length: μm ·Area measurement:Analyze Particles Size:100-Infinity(μm 2 ), check Include Holes and Summarize. Under the above image analysis conditions, the %Area value is calculated for each of the images taken from any three locations on the resin substrate 10, and the arithmetic mean value of these %Area values ​​is taken as the black area ratio.

[0044] The black area ratio in this specification is calculated by observing the plane of one surface 12 of the resin substrate 10. Therefore, compared to conventional surface roughness measurements, the surface condition can be observed in terms of a plane rather than a line.

[0045] Conventional surface roughness values ​​vary depending on the measurement method and range. If the measurement area is small, the roughness may be underestimated because the few protrusions are not measured. Also, even when measuring roughness over a linear range of a certain length, such as with the centerline average roughness, if large protrusions are measured, the roughness will be overestimated, but if not, the roughness will still be underestimated.

[0046] As described herein, by defining the surface condition of the resin substrate by the black area ratio, the surface condition of the resin substrate can be evaluated with reduced variation in the surface condition of the resin substrate, which makes it possible to suppress variation in the oxygen barrier property and more easily improve the oxygen barrier property of the gas barrier film 1.

[0047] Controlling the black area ratio by binarising optical microscope images is suitable for controlling oxygen barrier properties and printability, as it has a wide measurement range and allows protrusions to be found using a simple method.

[0048] The thickness of the resin substrate 10 is not particularly limited and is appropriately selected according to the price and application, taking into consideration suitability as a packaging material and suitability for laminating other films. The thickness of the resin substrate 10 is preferably 3 μm to 200 μm in practice, more preferably 5 μm to 120 μm, even more preferably 6 μm to 100 μm, and particularly preferably 10 μm to 30 μm.

[0049] <Underlayer> The underlayer 30 is provided between the resin substrate 10 and the inorganic oxide layer 40 or the oxygen barrier film 20 .

[0050] The base layer 30 is a layer containing an organic polymer as a main component and is sometimes called a primer layer. The provision of the base layer 30 can improve the film-forming properties and adhesion strength of the inorganic oxide layer 40 or the oxygen barrier coating 20.

[0051] The content of the organic polymer in the underlayer 30 may be, for example, 70% by mass or more, or 80% by mass or more. Examples of organic polymers include polyacrylic resin, polyester resin, polycarbonate resin, polyurethane resin, polyamide resin, polyolefin resin, polyimide resin, melamine resin, and phenolic resin. In consideration of the hot water resistance of the adhesive strength between the resin substrate 10 and the inorganic oxide layer 40 or the oxygen barrier coating 20, the underlayer 30 preferably contains at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these organic polymers. The underlayer 30 may also contain a silane coupling agent, an organic titanate, or a modified silicone oil.

[0052] More preferred examples of the organic polymer include an organic polymer having a urethane bond formed by the reaction of a polyol having two or more hydroxyl groups at the polymer terminal with an isocyanate compound, and / or an organic polymer containing a reaction product of a polyol having two or more hydroxyl groups at the polymer terminal with an organic silane compound such as a silane coupling agent or a hydrolyzate thereof.

[0053] Examples of polyols include at least one selected from acrylic polyol, polyvinyl acetal, polystyrene polyol, and polyurethane polyol. The acrylic polyol may be obtained by polymerizing an acrylic acid derivative monomer, or may be obtained by copolymerizing an acrylic acid derivative monomer with another monomer. Examples of the acrylic acid derivative monomer include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of the monomer copolymerized with the acrylic acid derivative monomer include styrene.

[0054] The isocyanate compound reacts with the polyol to form a urethane bond, thereby enhancing the adhesion between the resin substrate 10 and the inorganic oxide layer 40 or the oxygen barrier coating 20. In other words, the isocyanate compound functions as a crosslinking agent or curing agent. Examples of isocyanate compounds include aromatic monomers such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic monomers such as xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI), as well as polymers and derivatives thereof. The above-mentioned isocyanate compounds may be used alone or in combination.

[0055] Examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. The organic silane compound may contain one of the above-mentioned silane coupling agents and hydrolysates thereof, or two or more of them in combination.

[0056] The underlayer 30 can be formed by preparing a mixed solution by blending the above-mentioned components in an organic solvent in any ratio, and then applying the prepared mixed solution to one surface 12 of the resin substrate 10. The mixed solution may contain, for example, a curing accelerator such as a tertiary amine, an imidazole derivative, a metal salt compound of a carboxylic acid, a quaternary ammonium salt, or a quaternary phosphonium salt; an antioxidant such as a phenol-based, sulfur-based, or phosphite-based antioxidant; a leveling agent; a flow adjuster; a catalyst; a crosslinking reaction accelerator; a filler; etc.

[0057] The mixed liquid can be coated onto the resin substrate 10 using a known printing method such as offset printing, gravure printing, or silk screen printing, or a known application method such as roll coating, knife edge coating, or gravure coating. After coating, the mixture can be heated to, for example, 50 to 200°C, and dried and / or cured to form the underlayer 30.

[0058] The thickness of the underlayer 30 is not particularly limited and may be, for example, 0.005 to 5 μm. The thickness may be adjusted depending on the application or the desired properties. The thickness of the underlayer 30 is preferably 0.01 to 1 μm, and more preferably 0.01 to 0.5 μm. If the thickness of the underlayer 30 is 0.01 μm or more, sufficient adhesion strength is obtained between the resin substrate 10 and the inorganic oxide layer 40 or the oxygen barrier film 20, and the oxygen barrier properties are also good. If the thickness of the underlayer 30 is 1 μm or less, it is easy to form a uniform coated surface, and drying load and production costs can be reduced.

[0059] <Inorganic oxide layer> Examples of the inorganic oxide layer 40 include aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, tin oxide, zinc oxide, and indium oxide, and aluminum oxide or silicon oxide is particularly preferred because of its excellent productivity and excellent oxygen barrier and water vapor barrier properties in heat resistance and moist heat resistance. The inorganic oxide layer 40 may contain one of these oxides alone or two or more of them in combination.

[0060] The thickness of the inorganic oxide layer 40 is preferably 1 to 200 nm. If the thickness is 1 nm or more, excellent oxygen barrier properties and water vapor barrier properties are obtained, and if the thickness is 200 nm or less, the manufacturing cost can be kept low, cracks due to external forces such as bending or pulling are less likely to occur, and deterioration of the barrier properties can be suppressed.

[0061] The inorganic oxide layer 40 can be formed by a known film formation method such as vacuum deposition, sputtering, ion plating, or plasma vapor deposition (CVD).

[0062] <Oxygen barrier coating> The oxygen barrier film 20 may be a known oxygen barrier film formed by a wet coating method. The oxygen barrier film 20 is obtained by forming a coating film made of a coating agent on the underlayer 30 or the inorganic oxide layer 40 by a wet coating method, and then drying the coating film. The coating film is a wet film, and the film is a dry film.

[0063] The oxygen barrier film 20 is preferably a film containing a water-soluble polymer and at least one of a metal alkoxide, its hydrolysate, or its reaction product (organic-inorganic composite film), and more preferably a film further containing at least one of a silane coupling agent and its hydrolysate.

[0064] Examples of metal alkoxides and their hydrolysates contained in the organic-inorganic composite film include those represented by the general formula M(OR)n, such as tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(OC3H7)3], and their hydrolysates. One of these may be contained alone, or two or more may be contained in combination.

[0065] The total content of at least one of the metal alkoxide, its hydrolysate, and / or its reaction product in the organic-inorganic composite membrane is, for example, 40 to 70 mass%. From the viewpoint of further reducing oxygen permeability, the lower limit of the total content of at least one of the metal alkoxide, its hydrolysate, and / or its reaction product in the organic-inorganic composite membrane may be 50 mass%. From the same viewpoint, the upper limit of the total content of at least one of the metal alkoxide, its hydrolysate, and / or its reaction product in the organic-inorganic composite membrane may be 65 mass%.

[0066] The water-soluble polymer contained in the organic-inorganic composite film is not particularly limited, and examples thereof include polyvinyl alcohol-based polymers, polysaccharides such as starch, methyl cellulose, and carboxymethyl cellulose, and acrylic polyol-based polymers. From the viewpoint of further improving the oxygen gas barrier property, the water-soluble polymer preferably contains a polyvinyl alcohol-based polymer. The number-average molecular weight of the water-soluble polymer is, for example, 40,000 to 180,000.

[0067] A water-soluble polymer such as polyvinyl alcohol can be obtained by, for example, saponifying (including partial saponification) polyvinyl acetate. This water-soluble polymer may have several tens of percent or only a few percent of acetate groups remaining.

[0068] The content of the water-soluble polymer in the organic-inorganic composite membrane is, for example, 15 to 50 mass%. The lower limit of the content of the water-soluble polymer in the organic-inorganic composite membrane may be 20 mass% from the viewpoint of further reducing oxygen permeability. The upper limit of the content of the water-soluble polymer in the organic-inorganic composite membrane may be 45 mass% from the viewpoint of further reducing oxygen permeability.

[0069] Silane coupling agents and their hydrolysates contained in the organic-inorganic composite film include silane coupling agents having organic functional groups. Examples of such silane coupling agents and their hydrolysates include ethyltrimethoxysilane, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and their hydrolysates. One of these may be contained alone, or two or more may be contained in combination.

[0070] At least one of the silane coupling agent and its hydrolysate preferably has an epoxy group as an organic functional group. Examples of silane coupling agents having an epoxy group include γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The silane coupling agent having an epoxy group and its hydrolysate may have an organic functional group other than the epoxy group, such as a vinyl group, an amino group, a methacryl group, or a ureyl group.

[0071] The silane coupling agent having an organic functional group and its hydrolysate can further improve the oxygen barrier properties of the oxygen barrier coating 20 and its adhesion to the underlayer 30 or the inorganic oxide layer 40 through interaction between the organic functional group and the hydroxyl group of the water-soluble polymer. In particular, the epoxy groups of the silane coupling agent and its hydrolysate can interact with the hydroxyl groups of polyvinyl alcohol to form an oxygen barrier coating 20 that is particularly excellent in oxygen barrier properties and adhesion to the underlayer 30 or the inorganic oxide layer 40.

[0072] The total content of at least one of the silane coupling agent and its hydrolysate and / or reaction product thereof in the organic-inorganic composite film is, for example, 1 to 15 mass%. From the viewpoint of further reducing oxygen permeability, the lower limit of the total content of at least one of the silane coupling agent and its hydrolysate and / or reaction product thereof in the organic-inorganic composite film may be 2 mass%. From the same viewpoint, the upper limit of the total content of at least one of the silane coupling agent and its hydrolysate and / or reaction product thereof in the organic-inorganic composite film may be 12 mass%.

[0073] The organic-inorganic composite film may contain a crystalline inorganic layered compound having a layered structure. Examples of the inorganic layered compound include clay minerals such as kaolinite, smectite, and mica. One of these may be used alone, or two or more may be used in combination. The particle size of the inorganic layered compound is, for example, 0.1 to 10 μm. The aspect ratio of the inorganic layered compound is, for example, 50 to 5,000.

[0074] As the inorganic layered compound, a smectite clay mineral is preferred because it can form a film with excellent oxygen barrier properties and adhesive strength by allowing a water-soluble polymer to penetrate between the layers of the layered structure (intercalation).Specific examples of smectite clay minerals include montmorillonite, hectorite, saponite, and water-swellable synthetic mica.

[0075] Another preferred example of the oxygen barrier film 20 is a film containing a polyvalent metal salt of carboxylic acid, which is a reaction product between the carboxyl groups of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) (a polyvalent metal salt of polycarboxylic acid film). In this case, the film may be formed by applying a coating agent containing a mixture of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) and drying it under heat, or it may be formed by applying a coating agent containing a polycarboxylic acid polymer (A) as the main component and drying it to form a film A, applying a coating agent containing a polyvalent metal compound (B) as the main component, and drying it to form a film B, and then causing a crosslinking reaction between the A and B layers.

[0076] [Polycarboxylic acid polymer (A)] A polycarboxylic acid polymer is a polymer having two or more carboxyl groups in its molecule. Examples of polycarboxylic acid polymers include (co)polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids with other ethylenically unsaturated monomers; and acidic polysaccharides having a carboxyl group in their molecules, such as alginic acid, carboxymethyl cellulose, and pectin. Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include saturated carboxylic acid vinyl esters such as ethylene, propylene, and vinyl acetate, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamide, and acrylonitrile. These polycarboxylic acid polymers may be used alone or in combination of two or more.

[0077] Among the above-mentioned components, from the viewpoint of the gas barrier properties of the resulting gas barrier film 1, polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid, and crotonic acid are preferred, and polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid are particularly preferred. In such polymers, the proportion of structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid is preferably 80 mol% or more, and more preferably 90 mol% or more (where the total of all structural units constituting the polymer is taken as 100 mol%). The polymer may be a homopolymer or a copolymer. When the polymer is a copolymer containing structural units other than the above-mentioned structural units, examples of such structural units include structural units derived from the aforementioned ethylenically unsaturated monomers copolymerizable with the ethylenically unsaturated carboxylic acid.

[0078] The number-average molecular weight of the polycarboxylic acid polymer is preferably in the range of 2,000 to 10,000,000, and more preferably 5,000 to 1,000,000. If the number-average molecular weight is less than 2,000, the resulting gas barrier film will not achieve sufficient water resistance, and moisture may deteriorate the gas barrier properties and transparency, or whitening may occur. On the other hand, if the number-average molecular weight exceeds 10,000,000, the viscosity of the coating agent used to form the oxygen barrier film 20 may increase, impairing coatability. The number-average molecular weight is the polystyrene-equivalent number-average molecular weight determined by gel permeation chromatography (GPC).

[0079] When a coating agent containing a polycarboxylic acid polymer (A) as a main component is applied and dried to form a coating A, and then a coating B is formed, some of the carboxy groups of the polycarboxylic acid polymer may be neutralized in advance with a basic compound. By neutralizing some of the carboxy groups of the polycarboxylic acid polymer in advance, the water resistance and heat resistance of the coating A can be further improved. The basic compound is preferably at least one basic compound selected from the group consisting of polyvalent metal compounds, monovalent metal compounds, and ammonia. As the polyvalent metal compound, compounds exemplified in the description of the polyvalent metal compound (B) below can be used. Examples of monovalent metal compounds include sodium hydroxide and potassium hydroxide.

[0080] Various additives can be added to the coating agent containing the polycarboxylic acid polymer (A) as the main component, and examples of such additives include crosslinking agents, curing agents, leveling agents, antifoaming agents, antiblocking agents, antistatic agents, dispersants, surfactants, softeners, stabilizers, film-forming agents, and thickeners, provided that the barrier performance is not impaired.

[0081] The solvent used in the coating agent containing the polycarboxylic acid polymer (A) as the main component is preferably an aqueous medium. Examples of the aqueous medium include water, water-soluble or hydrophilic organic solvents, and mixtures thereof. The aqueous medium usually contains water or water as the main component. The water content in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more. Examples of the water-soluble or hydrophilic organic solvent include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, cellosolves, carbitols, and nitriles such as acetonitrile.

[0082] [Polyvalent metal compounds (B)] The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with the carboxyl groups of the polycarboxylic acid polymer to form a polyvalent metal salt of polycarboxylic acid, and examples thereof include zinc oxide particles, magnesium oxide particles, magnesium methoxide, copper oxide, calcium carbonate, etc. These may be used alone or in combination. Zinc oxide is preferred from the viewpoint of the oxygen barrier properties of the oxygen barrier coating.

[0083] Zinc oxide is an inorganic material capable of absorbing ultraviolet light. The average particle size of the zinc oxide particles is not particularly limited, but from the viewpoints of gas barrier properties, transparency, and coating suitability, the average particle size is preferably 5 μm or less, more preferably 1 μm or less, and particularly preferably 0.1 μm or less.

[0084] When a coating agent containing a polyvalent metal compound (B) as a main component is applied and dried to form a film, various additives may be added in addition to zinc oxide particles as needed, provided that the effects of the present disclosure are not impaired. Such additives may include a resin soluble or dispersible in the solvent used in the coating agent, a dispersant soluble or dispersible in the solvent, a surfactant, a softener, a stabilizer, a film-forming agent, a thickener, etc.

[0085] Among the above, the solvent used in the coating agent preferably contains a resin that is soluble or dispersible in the solvent. This improves the coatability and film-forming properties of the coating agent. Examples of such resins include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenolic resins, amino resins, fluororesins, epoxy resins, and isocyanate resins.

[0086] It is also preferable to contain a dispersant that is soluble or dispersible in the solvent used in the coating agent. This improves the dispersibility of the polyvalent metal compound. Anionic surfactants or nonionic surfactants can be used as the dispersant. Examples of such surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, alkyl phosphates, aromatic phosphate esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, alkyl allyl sulfate esters, polyoxyethylene alkyl phosphate esters, sorbitan alkyl esters, glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, polyoxyethylene sorbitol fatty acid esters, polyoxy fatty acid esters, and polyoxyethylene alkylamines. These surfactants may be used alone or in combination.

[0087] When an additive is contained in a coating agent containing a polyvalent metal compound (B) as a main component, the mass ratio of the polyvalent metal compound to the additive (polyvalent metal compound:additive) is preferably within a range of 30:70 to 99:1, and more preferably within a range of 50:50 to 98:2.

[0088] Examples of solvents used in coating agents containing a polyvalent metal compound (B) as a main component include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of coatability, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of manufacturability, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[0089] When a coating agent containing a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) is applied and dried to form a polycarboxylic acid polyvalent metal salt film, the polycarboxylic acid polyvalent metal salt film can be formed by mixing the polycarboxylic acid polymer (A), the polyvalent metal compound (B), a resin or dispersant soluble or dispersible in water or an alcohol as a solvent, and additives as needed, and applying and drying the resulting coating agent by a known coating method. Examples of coating methods include casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metaling bar coating, chamber doctor combined coating, and curtain coating.

[0090] The thickness of the oxygen barrier film 20 is set depending on the required oxygen barrier properties and may be, for example, 0.05 to 5 μm. The thickness of the oxygen barrier film 20 is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.5 μm. If the thickness of the oxygen barrier film 20 is 0.05 μm or more, sufficient oxygen barrier properties are likely to be obtained. If the thickness of the oxygen barrier film 20 is 1 μm or less, it is easy to form a uniform coated surface, drying load and production costs can be reduced, and the usefulness of using a resin substrate 10 having a surface with a black area ratio of 0.15% or less, which is a feature of the present disclosure, is enhanced.

[0091] A gas barrier film having the organic-inorganic composite film or the polyvalent metal salt film of polycarboxylic acid as the oxygen barrier film 20 exhibits excellent oxygen barrier properties even when subjected to boiling or retort sterilization, and when laminated with a sealant film, has sufficient adhesion strength and sealing strength to be used as a packaging material for boiling or retort treatment.Furthermore, it has advantages such as transparency not found in metal foils or metal vapor-deposited films, excellent bending resistance and stretching resistance, and no risk of generating harmful substances such as dioxins.

[0092] [Method for manufacturing gas barrier film] The gas barrier film 1 can be produced by forming an underlayer 30, an inorganic oxide layer 40, or both the underlayer 30 and the inorganic oxide layer 40 on one surface 12 of a resin substrate 10, and then forming an oxygen barrier coating 20 on the underlayer 30 or the inorganic oxide layer 40.

[0093] The method for producing the gas barrier film 1 of the present disclosure includes, for example, a selection step, a base layer forming step, an inorganic oxide layer forming step, and an oxygen barrier coating forming step.

[0094] The selection step may include, for example, selecting a resin substrate raw sheet having a surface black area ratio of 0.15% or less as the resin substrate. The surface black area ratio of the resin substrate raw sheet is measured by the same method as the above-described method for measuring the black area ratio of one surface 12 of the resin substrate 10.

[0095] The resin substrate 10 may be a commercially available product or may be manufactured by a known method.

[0096] An example of the underlayer formation process is a process in which a coating agent is applied to at least one surface 12 of the resin substrate 10 by a wet coating method to form a coating film, and the coating film is dried (to remove the solvent) to form the underlayer 30.

[0097] The coating agent can be applied by a known wet coating method, such as roll coating, gravure coating, reverse coating, die coating, screen printing, or spray coating.

[0098] The coating film made of the coating agent can be dried by known drying methods such as hot air drying, heat roll drying, infrared irradiation, etc. The drying temperature for the coating film is preferably, for example, 50 to 200° C. The drying time varies depending on the thickness of the coating film, the drying temperature, etc., but is preferably, for example, 1 second to 5 minutes.

[0099] The inorganic oxide layer forming process may be, for example, a process of forming an inorganic oxide layer 40 on one surface 12 of the resin substrate 10 or on the underlayer 30 by the above-mentioned vacuum deposition method, sputtering method, ion plating method, plasma vapor deposition (CVD), or the like.

[0100] An example of the oxygen barrier film forming process is a process in which a coating agent is applied onto the underlayer 30 or the inorganic oxide layer 40 by a wet coating method to form a coating film, and the coating film is dried (to remove the solvent) to form the oxygen barrier film 20.

[0101] The coating agent can be applied by a known wet coating method, such as roll coating, gravure coating, reverse coating, die coating, screen printing, or spray coating.

[0102] The coating film made of the coating agent can be dried by known drying methods such as hot air drying, heat roll drying, infrared irradiation, etc. The drying temperature for the coating film is preferably, for example, 50 to 200° C. The drying time varies depending on the thickness of the coating film, the drying temperature, etc., but is preferably, for example, 1 second to 5 minutes.

[0103] The oxygen barrier film 20 may be formed by a single application and drying process, or by repeated application and drying of the same or different coating agents multiple times.

[0104] In the underlayer forming step, inorganic oxide layer forming step, and oxygen barrier film forming step, the underlayer 30, inorganic oxide layer 40, or oxygen barrier film 20 is formed on one surface 12 of the resin substrate 10. In this case, the black area ratio of the one surface 12 is 0.15% or less. Furthermore, the underlayer 30, inorganic oxide layer 40, or oxygen barrier film 20 may be formed on both surfaces of the resin substrate 10. In this case, the black area ratio of the other surface 14 of the resin substrate 10 is 0.15% or less.

[0105] When forming the undercoat layer 30, inorganic oxide layer 40, or oxygen barrier film 20 on both sides of the resin substrate raw sheet, it is preferable that the black area ratio on both sides of the resin substrate raw sheet is 0.15% or less, as this further enhances the oxygen barrier properties and improves printability.

[0106] When the method for producing a gas barrier film 1 according to the present disclosure includes a selection step, a resin substrate having a surface black area ratio of 0.15% or less can be efficiently used. Therefore, by including the selection step, a gas barrier film 1 with improved oxygen barrier properties can be efficiently produced. Additionally, by including the selection step, a gas barrier film 1 with good printability can be efficiently produced.

[0107] The gas barrier film 1 of the present disclosure may further include a printing layer, a protective layer, a light-shielding layer, an adhesive layer, a heat-sealable thermal adhesive layer, and other functional layers, as needed.

[0108] When the gas barrier film 1 of the present disclosure has a heat-sealable heat-sealable layer, this heat-sealable layer is disposed on at least one outermost layer of the gas barrier film 1. By having the heat-sealable layer, the gas barrier film 1 becomes something that can be sealed by heat sealing (for example, a package or a lid).

[0109] The heat-sealing layer can be formed, for example, by laminating a laminate obtained by forming the underlayer 30 of this embodiment, the inorganic oxide layer 40, and the oxygen barrier coating 20 on one or both sides of a resin substrate with a known adhesive such as a polyurethane-based, polyester-based, or polyether-based adhesive by a known dry lamination method, extrusion lamination method, or the like.

[0110] <Action and effect> The gas barrier film 1 of the present disclosure binarizes the brightness of a monochrome image and 2 The total area ratio (black area ratio) of the black regions of the above sizes is calculated. On at least one surface of the resin substrate 10 having a black area ratio of 0.15% or less, an oxygen barrier film 20 is laminated via the base layer 30, the inorganic oxide layer 40, or both the base layer 30 and the inorganic oxide layer 40.

[0111] The gas barrier film 1 of the present disclosure has an oxygen barrier coating 20 formed on the surface of a resin substrate 10 with a black area ratio of 0.15% or less, via an underlayer 30, an inorganic oxide layer 40, or both, thereby making it less likely for film defects to occur due to large protrusions on the substrate surface and more likely to improve oxygen barrier properties.In addition, the printability of the gas barrier film 1 can be more easily improved.

[0112] Therefore, by using the gas barrier film 1 of the present disclosure as a packaging material, the quality preservation of the contents can be improved at low cost.

[0113] In addition, by using the gas barrier film 1 of the present disclosure as a packaging material, printing can be easily and beautifully applied.

[0114] (Embodiment 2) As described above, gas barrier films in which a coating is formed on the surface of a resin substrate by a wet coating method, a vapor deposition method, a sputtering method, or the like, have sometimes exhibited unstable oxygen barrier properties depending on the production lot. Specifically, the oxygen barrier properties of the gas barrier film have sometimes been inferior to the inherent oxygen barrier properties, i.e., the oxygen barrier properties expected from the material constituting the coating and the thickness of the coating. In particular, such problems tend to occur more easily when the coating thickness is thin. As a result, it has been necessary to address this issue by increasing the thickness of the gas barrier layer more than necessary, which has led to problems of poor productivity and excessive material costs.

[0115] Furthermore, polyolefin resin films are inexpensive and have high water vapor barrier properties as resin substrates, and are therefore often used as packaging materials. However, they have the drawback of poor adhesion to gas barrier coatings, resulting in poor laminate strength when laminated with a heat-sealable resin film to form a gas barrier packaging material.

[0116] The second embodiment aims to provide a gas barrier film that exhibits excellent gas barrier properties by fully exhibiting its inherent oxygen barrier properties even when the thickness of the coating for imparting oxygen barrier properties is thin, and that has sufficient adhesive strength for use as a packaging material, and a method for producing the same.

[0117] To investigate the cause of the above-mentioned problem, the inventors conducted detailed observations of the surface and cross section of gas barrier films with poor oxygen barrier properties using optical and electron microscopes. Cross-sectional electron microscope observations using a focused ion / electron beam processing and observation device were performed at locations where an antiblocking agent (hereinafter also referred to as "AB agent"), which is added to prevent blocking of the resin substrate, was present. The results confirmed that defects several micrometers in width had occurred in the coating at locations where the AB agent protruded. (An example of a cross-sectional electron microscope image is shown in Figure 8.) It is believed that these film defects acted as pathways for gas permeation, resulting in insufficient oxygen barrier properties. The AB agent caused protrusions of various sizes on the surface of the resin substrate. The protrusion height and density of the AB agent varied depending on the production lot of the resin substrate. It is believed that when a gas barrier film (oxygen barrier film) was coated on the surface of the resin substrate, the film was not formed locally at the locations of the large protrusions, resulting in defects and unstable oxygen barrier properties.

[0118] Therefore, the present inventors have devised a method for accurately determining, in a short time, the surface condition of a wide range of a resin substrate, which affects the oxygen barrier properties of a gas barrier film, and have arrived at the present disclosure.

[0119] [1] A resin substrate and an oxygen barrier coating formed on a first surface of the resin substrate, wherein at least one of an underlayer and an inorganic oxide layer is present between the resin substrate and the oxygen barrier coating; the resin substrate has two or more resin layers, and of the two or more resin layers, the resin layer forming the first surface is made of a polyolefin copolymer resin; and the first surface has protrusions with a Feret diameter of 8 μm or more at a rate of 20 / mm 2 The gas barrier film is as follows: <Measurement method> A white LED line light source is used to irradiate an arbitrary 36.6 mm square area on the first surface of the resin substrate with light at a light source distance of 100 mm and an incident angle of 83°. The transmitted light is then photographed at a measurement angle of 90° with a monochrome line camera to obtain a captured image. An analysis image of 3551 pixels x 5684 pixels (2.5 x 4.0 mm) is then cut out from the photographed image, and protrusions with a Feret's diameter of 8 μm or more are counted in the analysis image.

[0120] [2] A gas barrier film wherein the resin substrate is a polyolefin resin.

[0121] [3] A gas barrier film, wherein the thickness of the underlayer is 0.01 to 1 μm.

[0122] [4] A gas barrier film in which the underlayer contains an organic polymer as a main component, and the organic polymer contains at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these organic polymers.

[0123] [5] A gas barrier film, wherein the inorganic oxide layer has a thickness of 1 to 200 nm.

[0124] [6] A gas barrier film, wherein the inorganic oxide layer is aluminum oxide or silicon oxide.

[0125] [7] A gas barrier film, wherein the oxygen barrier coating has a thickness of 0.05 to 1 μm.

[0126] [8] The oxygen barrier film is formed from at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a reaction product of a metal alkoxide or a hydrolyzate of a metal alkoxide. and a water-soluble polymer.

[0127] [9] A gas barrier film, wherein the oxygen barrier coating further contains at least one of a silane coupling agent, a hydrolysate of a silane coupling agent, and a reaction product of a silane coupling agent or a hydrolysate of a silane coupling agent.

[0128]

[10] A gas barrier film, wherein the oxygen barrier coating contains a polyvalent metal salt of a carboxylic acid, which is a reaction product between a carboxyl group of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B).

[0129]

[11] In the method for producing a gas barrier film according to any one of [1] to

[10] , the number of protrusions on one surface of a raw resin substrate is measured by the following measurement method, and the number of protrusions having a Feret's diameter of 8 μm or more is 20 / mm 2 A method for producing a gas barrier film, comprising the steps of: forming a resin substrate from a raw resin substrate as described below; and applying a coating agent to at least a first surface of the resin substrate to form an oxygen barrier film. <Measurement method> A white LED line light source is used to irradiate an arbitrary 36.6 mm square area on the first surface of the resin substrate with light at a light source distance of 100 mm and an incident angle of 83°. The transmitted light is then photographed at a measurement angle of 90° with a monochrome line camera to obtain a captured image. An analysis image of 3551 pixels x 5684 pixels (2.5 x 4.0 mm) is then cut out from the photographed image, and protrusions with a Feret's diameter of 8 μm or more are counted in the analysis image.

[0130] The gas barrier film of the present disclosure will be described with reference to an embodiment. FIG. 4 is a schematic cross-sectional view of a gas barrier film 101 according to embodiment 2. The dimensional ratios in FIG. 4 are different from the actual ratios for ease of explanation. The gas barrier film 101 has a resin substrate 120, an underlayer 140, an inorganic oxide layer 150, and an oxygen barrier coating 130. Note that either the underlayer 140 or the inorganic oxide layer 150 may be omitted. The underlayer 140 is laminated in contact with the first surface 21 of the resin substrate 120, and the inorganic oxide layer 150 is laminated on the surface of the underlayer 140 opposite the surface that is in contact with the resin substrate 120. The inorganic oxide layer 150 is laminated in contact with the underlayer 140, and the oxygen barrier coating 130 is located in contact with the surface of the inorganic oxide layer 150 opposite the surface that is in contact with the underlayer 140. If the base layer 140 is not provided, the inorganic oxide layer 150 is laminated on the first surface 21 of the resin substrate 120. If the inorganic oxide layer 150 is not provided, the oxygen barrier film 130 is laminated on the base layer 140.

[0131] <Resin substrate> The resin substrate 120 has two or more resin layers including a base layer 25. In this embodiment, the resin substrate 120 has the base layer 25 and a surface layer 23 located on one surface of the base layer 25. The surface layer 23 forms a first surface 21 of the resin substrate 120. The resin substrate 120 contains a resin, and each layer of the surface layer 23 and base layer 25 that constitute the resin substrate 120 also contains a resin.

[0132] The base layer 25 adjusts the mechanical properties, chemical properties, thermal properties, optical properties, etc. of the resin substrate 120. Mechanical properties include rigidity, elongation, stiffness, tear strength, impact strength, puncture strength, pinhole resistance, etc. Chemical properties include water vapor barrier properties, gas barrier properties, aroma retention, chemical resistance, oil resistance, etc. Thermal properties include melting point, glass transition point, heat resistance temperature, cold resistance temperature, thermal shrinkage rate, etc. Optical properties include transparency, gloss, etc.

[0133] The resin used as the raw material for the base layer 25 is preferably a polyolefin resin from the viewpoints of ease of availability and water vapor barrier properties. Examples of polyolefin resins include polyethylene, polypropylene, and polybutene. Polypropylene may be a homopolymer, random copolymer, or block copolymer. A homopolymer is a polypropylene consisting solely of propylene. A random copolymer is a polypropylene in which the main monomer propylene is randomly copolymerized with a different type of comonomer to form a homogeneous phase. A block copolymer is a polypropylene in which the main monomer propylene and the above comonomer are copolymerized in a block manner or polymerized into a rubber-like form to form a heterogeneous phase. Any one of these polyolefin resins may be used alone, or two or more may be blended together.

[0134] The base layer 25 may contain an additive. The additive can be appropriately selected from various known additives. Examples of the additive include fillers, antiblocking agents (AB agents), heat stabilizers, weather stabilizers, UV absorbers, lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, and dyes. Any one of these additives may be used alone, or two or more may be used in combination. The content of the additive in the base layer 25 can be appropriately adjusted within a range that does not interfere with the effects of the present disclosure.

[0135] The base layer 25 may have a single layer structure or a multi-layer structure. The thickness of the base layer 25 may be, for example, 3 to 200 μm, or 6 to 30 μm.

[0136] The surface layer 23 is composed of a polyolefin copolymer resin. Examples of polyolefin copolymer resins include ethylene-propylene copolymers, ethylene-1-butene copolymers, propylene-1-butene copolymers, propylene-pentene copolymers, ethylene-propylene-1-butene copolymers, ethylene-acrylic acid copolymers, ionomers obtained by crosslinking ethylene-acrylic acid copolymers with metal ions, and propylene-acrylic acid copolymers. Each of these resins may be a random copolymer or a block copolymer. These resins may be used alone or in a blend of two or more. By comprising the surface layer 23 as a polyolefin copolymer resin, good adhesion can be achieved with the underlayer 140, inorganic oxide layer 150, or oxygen barrier coating 130, which are laminated on the resin substrate 120.

[0137] The surface layer 23 may contain an additive. The additive can be appropriately selected from various known additives. Examples of the additive include an antiblocking agent (AB agent), a heat stabilizer, a weather stabilizer, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antistatic agent, an antifogging agent, a pigment, and a dye. Any one of these additives may be used alone, or two or more may be used in combination. The content of the additive in the surface layer 23 can be appropriately adjusted within a range that does not impair the effects of the present disclosure.

[0138] When the surface layer 23 contains an AB agent, protrusions resulting from the AB agent are formed on the first surface 21 of the resin substrate 120. These protrusions prevent adhesion of films to each other and improve the processability of the film roll when it is wound, unwound, and transported. In particular, the average particle size of the AB agent and its amount added affect the size and number of protrusions on the first surface 21, so it is recommended to use a method in which the number of protrusions on the first surface 21 is 20 / mm. 2 It is desirable to adjust it as follows:

[0139] The AB agent is a solid particle, and examples thereof include organic particles and inorganic particles. Examples of organic particles include polymethyl methacrylate particles, polystyrene particles, and polyamide particles. These organic particles are obtained, for example, by emulsion polymerization or suspension polymerization. Examples of inorganic particles include silica particles, zeolite, talc, kaolinite, and feldspar. These AB agents may be used alone or in combination of two or more. As the AB agent, polymethyl methacrylate particles are preferred among organic agents, and silica particles are preferred among inorganic agents.

[0140] The average particle size of the AB agent is preferably 0.1 μm or more and 5 μm or less. From the viewpoint of achieving both anti-blocking performance and gas barrier performance of the gas barrier film 101, the average particle size of the AB agent is particularly preferably 1 μm or more and 4 μm or less. The average particle size of the AB agent is measured by the Coulter method.

[0141] The amount of the AB agent added is preferably, for example, 0.05 to 0.4 mass % relative to the total mass of the surface layer 23. The amount of the AB agent added in the surface layer 23 is specifically calculated by the following formula. Amount of AB agent added [mass%] = {(i) / 100} × {(ii) / 100} × 100 In the formula, (i) indicates the concentration (mass %) of the AB agent in masterbatch resin chips obtained by adding an AB agent to a resin, stirring the mixture, kneading the mixture in an extruder, and melt-extruding the mixture into pellets. (ii) indicates the concentration (mass %) of the masterbatch resin chips containing the AB agent relative to the total mass of the resin pellets that make up surface layer 23 when the masterbatch resin chips containing the AB agent are blended with a resin that does not contain the AB agent. When the AB agent is added to base layer 25, the amount added is also preferably 0.05 to 0.4 mass % relative to the total mass of base layer 25, and the amount added can be calculated using the formula above.

[0142] The thickness of the surface layer 23 may be, for example, 0.1 to 10 μm, or may be 0.5 to 5.0 μm.

[0143] The resin substrate 120 is preferably a co-extruded film including at least a surface layer 23 and a base layer 25. The resin substrate 120 may be a stretched film or an unstretched film.

[0144] The resin substrate 120 preferably has a biaxially oriented polypropylene film. Biaxially oriented polypropylene film has particularly excellent water vapor barrier properties, so the inclusion of the biaxially oriented polypropylene film improves the water vapor barrier properties of the gas barrier film 101. The biaxially oriented polypropylene film may be a film formed from at least one of a homopolymer, a random copolymer, a block copolymer, or the like. The biaxially oriented polypropylene film is preferably a coextruded film.

[0145] The base layer 25 may be made of a biaxially oriented polypropylene film, or may be a laminate of a biaxially oriented polypropylene film and another resin film. Examples of other resin films include polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyolefin resin films such as polyethylene, polystyrene films, polyamide films such as nylon, polycarbonate films, polyacrylonitrile films, and engineering plastic films such as polyimide films.

[0146] The thickness of the resin substrate 120 is not particularly limited and is appropriately selected according to the price and application, taking into consideration suitability as a packaging material and suitability for laminating other films. The thickness of the resin substrate 120 is preferably 3 μm to 200 μm in practical terms, more preferably 5 μm to 120 μm, and even more preferably 6 μm to 30 μm.

[0147] The first surface 21 of the resin substrate 120 may be subjected to at least one treatment selected from the group consisting of chemical treatment, solvent treatment, corona treatment, plasma treatment, and ozone treatment.

[0148] When protrusions are formed on the first surface 21 of the resin substrate 120 by the AB agent, blocking of the film can be prevented. However, in the case of large protrusions, film defects that become paths for gas permeation are likely to occur in the undercoat layer 140, inorganic oxide layer 150, and oxygen barrier coating 130 formed thereon, which may reduce the oxygen barrier properties of the gas barrier film 101. However, the first surface 21 of the resin substrate 120 of the gas barrier film 101 of the present disclosure has protrusions with a Feret's diameter of 8 μm or more at a rate of 20 / mm 2 The first surface 21 of the resin substrate 120 has a density of protrusions with a Feret's diameter of 8 μm or more of 17 / mm 2 It is more preferable that the number of protrusions per mm is 15 or less, and that the number of protrusions per mm is 8 μm or more. 2 It is more preferable that the number of protrusions per mm is 0 or less, and that the number of protrusions per mm is 8 μm or more. 2Many of the protrusions with a Feret diameter of 8 μm or more have a height of more than 1 μm from the flat portion of the first surface 21 to the top of the protrusion, which makes them prone to causing film defects in the oxygen barrier coating. For this reason, the number of protrusions with a Feret diameter of 8 μm or more is limited to 20 / mm 2 If the number is less than this, film defects are less likely to occur in the underlayer 140, the inorganic oxide layer 150, and the oxygen barrier coating 130, which makes it easier to improve the oxygen barrier properties of the gas barrier film 101. The protrusions formed on the first surface 21 of the resin substrate 120 may be derived from the AB agent or from other factors, and are not particularly limited. In this specification, the number of protrusions on the first surface 21 of the resin substrate 120 is a value measured by the following measurement method.

[0149] <Measurement method> An arbitrary 36.6 mm square area of ​​the resin substrate 120 is irradiated with light from the second surface 22, which is the surface opposite to the first surface 21 of the resin substrate 120, at a light source distance of 100 mm and an incident angle of 83° using a white LED line light source. The transmitted light is captured at a measurement angle of 90° using a monochrome line camera to obtain a captured image. An analysis image of 3551 pixels x 5684 pixels (2.5 x 4.0 mm) is cut out from the captured image. Protrusions with a Feret's diameter of 8 μm or more are extracted from the cut-out analysis image using image analysis software, and the number of protrusions is counted. 2 This is calculated as the number of protrusions with a Feret diameter of 8 μm or more per particle.

[0150] A method for measuring the number of protrusions on the first surface 21 of the resin base material 120 will be described below with reference to the drawings. First, the measuring device will be described.

[0151] (Measuring equipment) As shown in FIG. 5, a measuring device 15 for measuring the number of protrusions on a first surface 21 of a resin substrate 120 includes a sample holder 2, a light source 4, and a monochrome line camera 7. The sample holder 2 is placed on a transport device 16 and can move horizontally. A punched hole 3 is formed in the center of the sample holder 2. The light source 4 is located below the sample holder 2 at a light source distance of 100 mm, and is connected to a light source control device 6. The monochrome line camera 7 is located above the sample holder 2, and is equipped with a macro lens 8. An image processing device 9 is connected to the image processing device 9. A transport control unit 17 is connected to the transport device 16.

[0152] There are no particular limitations on the sample holder 2 as long as it is flat and horizontal, and any known holder may be used. The light source 4 is preferably a white LED line light source that emits visible light.

[0153] The monochrome line camera 7 preferably has 16,384 pixels, with a sensor size of 3.52 μm per pixel. The monochrome line camera 7 is preferably controlled by the image processing device 9 via a standard interface such as Camera Link or USB. The image processing device 9 is composed of, for example, a personal computer equipped with a frame grabber or the like that connects to the monochrome line camera 7, and image processing software that controls the frame grabber. Personal computers equipped with frame grabbers or the like and image processing software that controls the frame grabber are widely distributed or commercially available, and these can be used as the image processing device 9. An example of image processing software is "ImageJ," a public domain software developed by the National Institutes of Health (NIH).

[0154] It is preferable to use a uniaxial stage driven by a stepping motor as the transport device 16. The transport device 16 is controlled by a transport control unit 17 in terms of transport speed, transport start, transport stop, and the like.

[0155] (Sample preparation) Next, a method for measuring the number of protrusions on the first surface of the resin substrate 120 will be described. As shown in Fig. 5, first, the first surface 21 of the resin substrate 120 is faced toward the monochrome line camera 7, and the resin substrate 120 is fixed to the sample holder 2 so that there are no height differences within the surface. When fixing the resin substrate 120, it is preferable to fix the edges of the resin substrate 120 using OPP tape, masking tape, or the like. The resin substrate 120 is fixed to the sample holder 2 so that the image measurement position 18 of the resin substrate 120 is aligned with the perforation 3.

[0156] (Acquisition of captured images) Next, a white LED line light is incident from the light source 4. The light intensity of the light source 4 can be adjusted using the light source control device 6. Preferably, the light intensity of the incident light L1 is adjusted using the light source control device 6 so that the light intensity at the image measurement position 18 is 442 lux. The incident light L1 from the light source 4 is incident at an angle of incidence 13 of 83° with respect to the first surface 21, tilted 7° from the vertical, and positioned so that the measurement angle 19 with respect to the first surface 21 is 90°. The transmitted light L2 that passes through the image measurement position 18 is captured by the monochrome line camera 7 via the macro lens 8. The magnification of the macro lens 8 is 5x, the F-number is 2.8, and the resolution is 0.704 μm. The measurement range of the monochrome line camera 7 at the image measurement position 18 is a 36.6 mm square area, and the effective illumination range of the light source 4 is at least 36.6 mm square.

[0157] The measurement range of the transmitted light L2 is a 36.6 mm square area of ​​the first surface 21. The conveying device 16 is moved so that the measurement range is the above-mentioned area. If the conveying device 16 is a stepping motor or the like, a pulse signal indicating the conveying speed is input to the image processing device 9. The conveying speed of the conveying device 16 is preferably set to be equal to the product of the spatial resolution and the capture frequency. The spatial resolution is determined by the sensor size (3.52 μm) of the monochrome line camera 7 and the magnification (5x) of the macro lens 8. The capture frequency is the capture frequency of one line of the monochrome line camera 7. The conveying speed is set to be equal to the product of the spatial resolution and the capture frequency, and the resin substrate 120 is continuously conveyed at the image measurement position 18 of the monochrome line camera 7. At the image measurement position 18, the monochrome line camera 7 measures and captures an image of the first surface 21 of the resin substrate 120.

[0158] The exposure time of the monochrome line camera 7 is set to 80 μs. The period of the capture frequency is set to be longer than the exposure time. The resin substrate 120 is conveyed, and a photographed image of 5684 pixels or more is acquired in the conveying direction of the resin substrate 120.

[0159] (Image analysis) From the captured image, the central 3551 pixels corresponding to the sensor arrangement direction of the monochrome line camera 7 (the direction perpendicular to the conveyance direction of the resin substrate 120) and 5684 pixels in the conveyance direction are cut out to create an image for analysis. It is also possible to cut out more than 5684 pixels in the conveyance direction to widen the measurement range. The cut-out image for analysis is analyzed using image analysis software.

[0160] Figure 6 shows the principle by which this measurement system can detect minute protrusions and depressions on the surface of the resin substrate 120. When the incident angle θ2 is reduced from the measurement angle θ1 using a line camera, the protrusions are visualized three-dimensionally, with the upper part of the image brighter and the lower part darker. The upside-down orientation is reversed in depressions. This is presumably due to refraction similar to that of a spherical lens. Using this tendency, bright and dark particles are selected and binarized from the analysis image based on brightness, size, and circularity, respectively, and particles that are bright on top and dark on the bottom are extracted as protrusions, and Feret diameter data for the extracted particles is obtained. Figure 7 shows a photographed image of the first surface 21 of the resin substrate 120 of the example, along with an analysis image in which the protrusions have been extracted using the above algorithm. From the Feret diameter data extracted in this way, the number of particles with a Feret diameter of 8 μm or more in the analysis image is counted, and the Feret diameter is calculated. 2 The value converted into the number per area was taken as the number of protrusions.

[0161] <Underlayer> The underlayer 140 is provided between the resin substrate 120 and the inorganic oxide layer 150 or the oxygen barrier coating 130. The underlayer 140 is a layer containing an organic polymer as a main component, and is sometimes called a primer layer. By providing the underlayer 140, the film-forming properties and adhesion strength of the inorganic oxide layer 150 or the oxygen barrier coating 130 can be improved.

[0162] The content of the organic polymer in the underlayer 140 may be, for example, 70% by mass or more, or 80% by mass or more. Examples of organic polymers include polyacrylic resin, polyester resin, polycarbonate resin, polyurethane resin, polyamide resin, polyolefin resin, polyimide resin, melamine resin, and phenolic resin. In consideration of the hot water resistance of the adhesive strength between the resin substrate 120 and the inorganic oxide layer 150 or the oxygen barrier coating 130, the underlayer 140 preferably contains at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these organic polymers. The underlayer 140 may also contain a silane coupling agent, an organic titanate, or a modified silicone oil.

[0163] More preferred examples of the organic polymer include an organic polymer having a urethane bond formed by the reaction of a polyol having two or more hydroxyl groups at the polymer terminal with an isocyanate compound, and / or an organic polymer containing a reaction product of a polyol having two or more hydroxyl groups at the polymer terminal with an organic silane compound such as a silane coupling agent or a hydrolyzate thereof.

[0164] Examples of polyols include at least one selected from acrylic polyol, polyvinyl acetal, polystyrene polyol, and polyurethane polyol. The acrylic polyol may be obtained by polymerizing an acrylic acid derivative monomer, or may be obtained by copolymerizing an acrylic acid derivative monomer with another monomer. Examples of the acrylic acid derivative monomer include ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Examples of the monomer copolymerized with the acrylic acid derivative monomer include styrene.

[0165] The isocyanate compound reacts with the polyol to form a urethane bond, which enhances the adhesion between the resin substrate 120 and the inorganic oxide layer 150 or the oxygen barrier coating 130. In other words, the isocyanate compound functions as a crosslinking agent or curing agent. Examples of isocyanate compounds include aromatic monomers such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic monomers such as xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI), as well as polymers and derivatives thereof. The above-mentioned isocyanate compounds may be used alone or in combination of two or more.

[0166] Examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. The organic silane compound may be a hydrolyzate of these silane coupling agents. The organic silane compound may contain one of the above-mentioned silane coupling agents and their hydrolyzates, or two or more of them in combination.

[0167] The underlayer 140 can be formed by preparing a mixed solution by blending the above-mentioned components in an organic solvent in any ratio, and using the prepared mixed solution on the first surface 21 of the resin substrate 120. The mixed solution may contain, for example, a curing accelerator such as a tertiary amine, an imidazole derivative, a metal salt compound of a carboxylic acid, a quaternary ammonium salt, or a quaternary phosphonium salt; an antioxidant such as a phenol-based, sulfur-based, or phosphite-based antioxidant; a leveling agent; a flow adjuster; a catalyst; a crosslinking reaction accelerator; a filler; etc.

[0168] The mixed liquid can be coated onto the resin substrate 120 using a known printing method such as offset printing, gravure printing, or silk screen printing, or a known application method such as roll coating, knife edge coating, or gravure coating. After coating, the mixture can be heated to, for example, 50 to 200°C, and dried and / or cured to form the underlayer 140.

[0169] The thickness of the underlayer 140 is not particularly limited and may be, for example, 0.005 to 5 μm. The thickness may be adjusted depending on the application or desired properties. The thickness of the underlayer 140 is preferably 0.01 to 1 μm, and more preferably 0.01 to 0.5 μm. If the thickness of the underlayer 140 is 0.01 μm or more, sufficient adhesion strength between the resin substrate 120 and the inorganic oxide layer 150 or the oxygen barrier film 130 is obtained, and the oxygen barrier properties are also good. If the thickness of the underlayer 140 is 1 μm or less, it is easy to form a uniform coated surface, and drying load and manufacturing costs can be reduced.

[0170] <Inorganic oxide layer> Examples of inorganic oxide layers 150 include aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, tin oxide, zinc oxide, and indium oxide. Aluminum oxide and silicon oxide are particularly preferred because of their excellent productivity and excellent oxygen and water vapor barrier properties in heat and moist heat resistance. The inorganic oxide layer 150 may contain one of these oxides alone or a combination of two or more. The thickness of the inorganic oxide layer 150 is preferably 1 to 200 nm. A thickness of 1 nm or more provides excellent oxygen and water vapor barrier properties. A thickness of 200 nm or less reduces manufacturing costs, reduces cracking due to external forces such as bending or pulling, and suppresses deterioration of barrier properties. The inorganic oxide layer 150 can be formed by known film formation methods, such as vacuum deposition, sputtering, ion plating, and plasma vapor deposition (CVD).

[0171] <Oxygen barrier coating> The oxygen barrier film 130 may be a known oxygen barrier film formed by a wet coating method. The oxygen barrier film 130 is obtained by forming a coating film made of a coating agent on the underlayer 140 or the inorganic oxide layer 150 by a wet coating method, and then drying the coating film. The coating film is a wet film, and the film is a dry film.

[0172] The oxygen barrier film 130 is preferably a film (organic-inorganic composite film) containing at least one of a metal alkoxide, its hydrolysate, or its reaction product, and a water-soluble polymer, and is further preferably a film further containing at least one of a silane coupling agent and its hydrolysate.

[0173] Examples of metal alkoxides and their hydrolysates contained in the organic-inorganic composite film include those represented by the general formula M(OR), such as tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(OC3H7)3]. nand hydrolysates thereof. One of these may be contained alone, or two or more may be contained in combination.

[0174] The total content of at least one of the metal alkoxide, its hydrolysate, and / or its reaction product in the organic-inorganic composite membrane is, for example, 40 to 70 mass%. From the viewpoint of further reducing oxygen permeability, the lower limit of the total content of at least one of the metal alkoxide, its hydrolysate, and / or its reaction product in the organic-inorganic composite membrane may be 50 mass%. From the same viewpoint, the upper limit of the total content of at least one of the metal alkoxide, its hydrolysate, and / or its reaction product in the organic-inorganic composite membrane may be 65 mass%.

[0175] The water-soluble polymer contained in the organic-inorganic composite film is not particularly limited, and examples thereof include polyvinyl alcohol-based polymers, polysaccharides such as starch, methyl cellulose, and carboxymethyl cellulose, and acrylic polyol-based polymers. From the viewpoint of further improving the oxygen gas barrier property, the water-soluble polymer preferably contains a polyvinyl alcohol-based polymer. The number-average molecular weight of the water-soluble polymer is, for example, 40,000 to 180,000.

[0176] A water-soluble polymer such as polyvinyl alcohol can be obtained by, for example, saponifying (including partial saponification) polyvinyl acetate. This water-soluble polymer may have several tens of percent or only a few percent of acetate groups remaining.

[0177] The content of the water-soluble polymer in the organic-inorganic composite membrane is, for example, 15 to 50 mass%. The lower limit of the content of the water-soluble polymer in the organic-inorganic composite membrane may be 20 mass% from the viewpoint of further reducing oxygen permeability. The upper limit of the content of the water-soluble polymer in the organic-inorganic composite membrane may be 45 mass% from the viewpoint of further reducing oxygen permeability.

[0178] Silane coupling agents and their hydrolysates contained in the organic-inorganic composite film include silane coupling agents having an organic functional group. Examples of such silane coupling agents and their hydrolysates include ethyltrimethoxysilane, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and their hydrolysates. One of these may be contained alone, or two or more may be contained in combination. .

[0179] At least one of the silane coupling agent and its hydrolysate preferably has an epoxy group as an organic functional group. Examples of silane coupling agents having an epoxy group include γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The silane coupling agent having an epoxy group and its hydrolysate may have an organic functional group other than the epoxy group, such as a vinyl group, an amino group, a methacryl group, or a ureyl group.

[0180] The silane coupling agent having an organic functional group and its hydrolysate can further improve the oxygen barrier properties of the oxygen barrier coating 130 and the adhesion to the base layer 140 or the inorganic oxide layer 150 through interaction between the organic functional group and the hydroxyl group of the water-soluble polymer. In particular, the epoxy groups of the silane coupling agent and its hydrolysate can interact with the hydroxyl groups of polyvinyl alcohol to form an oxygen barrier coating 130 that is particularly excellent in oxygen barrier properties and adhesion to the base layer 140 or the inorganic oxide layer 150.

[0181] The total content of at least one of the silane coupling agent and its hydrolysate and / or reaction product thereof in the organic-inorganic composite film is, for example, 1 to 15 mass%. From the viewpoint of further reducing oxygen permeability, the lower limit of the total content of at least one of the silane coupling agent and its hydrolysate and / or reaction product thereof in the organic-inorganic composite film may be 2 mass%. From the same viewpoint, the upper limit of the total content of at least one of the silane coupling agent and its hydrolysate and / or reaction product thereof in the organic-inorganic composite film may be 12 mass%.

[0182] The organic-inorganic composite film may contain a crystalline inorganic layered compound having a layered structure. Examples of the inorganic layered compound include clay minerals such as kaolinite, smectite, and mica. One of these may be used alone, or two or more may be used in combination. The particle size of the inorganic layered compound is, for example, 0.1 to 10 μm. The aspect ratio of the inorganic layered compound is, for example, 50 to 5,000.

[0183] As the inorganic layered compound, a smectite clay mineral is preferred because it can form a film with excellent oxygen barrier properties and adhesive strength by allowing a water-soluble polymer to penetrate between the layers of the layered structure (intercalation).Specific examples of smectite clay minerals include montmorillonite, hectorite, saponite, and water-swellable synthetic mica.

[0184] Another preferred example of the oxygen barrier film 130 is a film containing a polyvalent metal salt of carboxylic acid, which is a reaction product between the carboxyl groups of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) (a polyvalent metal salt of polycarboxylic acid film). In this case, the film may be a polyvalent metal salt of polycarboxylic acid film formed by applying a coating agent containing a mixture of a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) and drying it under heat, or a polyvalent metal salt of polycarboxylic acid film formed by applying a coating agent containing a polycarboxylic acid polymer (A) as the main component and drying it to form a film A, applying a coating agent containing a polyvalent metal compound (B) as the main component, and drying it to form a film B, and then causing a crosslinking reaction between the A and B layers.

[0185] [Polycarboxylic acid polymer (A)] A polycarboxylic acid polymer is a polymer having two or more carboxyl groups in its molecule. Examples of polycarboxylic acid polymers include (co)polymers of ethylenically unsaturated carboxylic acids; copolymers of ethylenically unsaturated carboxylic acids with other ethylenically unsaturated monomers; and acidic polysaccharides having a carboxyl group in their molecules, such as alginic acid, carboxymethyl cellulose, and pectin. Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include saturated carboxylic acid vinyl esters such as ethylene, propylene, and vinyl acetate, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamide, and acrylonitrile. These polycarboxylic acid polymers may be used alone or in combination of two or more.

[0186] Among the above-mentioned components, from the viewpoint of the gas barrier properties of the resulting gas barrier film, polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, itaconic acid, fumaric acid, and crotonic acid are preferred, and polymers containing structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid are particularly preferred. In such polymers, the proportion of structural units derived from at least one polymerizable monomer selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, and itaconic acid is preferably 80 mol% or more, more preferably 90 mol% or more (where the total of all structural units constituting the polymer is 100 mol%). The polymer may be a homopolymer or a copolymer. When the polymer is a copolymer containing structural units other than the above-mentioned structural units, examples of such structural units include structural units derived from the aforementioned ethylenically unsaturated monomer copolymerizable with the ethylenically unsaturated carboxylic acid.

[0187] The number-average molecular weight of the polycarboxylic acid polymer is preferably in the range of 2,000 to 10,000,000, and more preferably 5,000 to 1,000,000. If the number-average molecular weight is less than 2,000, the resulting gas barrier film will not achieve sufficient water resistance, and moisture may deteriorate the gas barrier properties and transparency, or whitening may occur. On the other hand, if the number-average molecular weight exceeds 10,000,000, the viscosity of the coating agent used to form the oxygen barrier film 130 may increase, impairing coatability. The number-average molecular weight is the polystyrene-equivalent number-average molecular weight determined by gel permeation chromatography (GPC).

[0188] When a coating agent containing a polycarboxylic acid polymer (A) as a main component is applied and dried to form a coating A, and then the coating B is formed, some of the carboxy groups of the polycarboxylic acid polymer may be neutralized in advance with a basic compound. By neutralizing some of the carboxy groups of the polycarboxylic acid polymer in advance, the water resistance and heat resistance of the coating A can be further improved. The basic compound is preferably at least one basic compound selected from the group consisting of polyvalent metal compounds, monovalent metal compounds, and ammonia. As the polyvalent metal compound, compounds exemplified in the description of the polyvalent metal compound (B) below can be used. Examples of monovalent metal compounds include sodium hydroxide and potassium hydroxide.

[0189] Various additives can be added to the coating agent containing the polycarboxylic acid polymer (A) as the main component. Examples of the additives include crosslinking agents, curing agents, leveling agents, antifoaming agents, antiblocking agents, antistatic agents, dispersants, surfactants, softeners, stabilizers, film-forming agents, thickeners, and the like, provided that the additives do not impair the barrier performance.

[0190] The solvent used in the coating agent containing the polycarboxylic acid polymer (A) as the main component is preferably an aqueous medium. Examples of the aqueous medium include water, water-soluble or hydrophilic organic solvents, and mixtures thereof. The aqueous medium usually contains water or water as the main component. The water content in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more. Examples of the water-soluble or hydrophilic organic solvent include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, cellosolves, carbitols, and nitriles such as acetonitrile.

[0191] [Polyvalent metal compounds (B)] The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with the carboxyl groups of the polycarboxylic acid polymer to form a polyvalent metal salt of polycarboxylic acid, and examples thereof include zinc oxide particles, magnesium oxide particles, magnesium methoxide, copper oxide, calcium carbonate, etc. These may be used alone or in combination. Zinc oxide is preferred from the viewpoint of the oxygen barrier properties of the oxygen barrier coating.

[0192] Zinc oxide is an inorganic material capable of absorbing ultraviolet light. The average particle size of the zinc oxide particles is not particularly limited, but from the viewpoints of gas barrier properties, transparency, and coating suitability, the average particle size is preferably 5 μm or less, more preferably 1 μm or less, and particularly preferably 0.1 μm or less.

[0193] When a coating agent containing a polyvalent metal compound (B) as a main component is applied and dried to form a B film, various additives may be added in addition to zinc oxide particles as needed, provided that the effects of the present disclosure are not impaired. Such additives may include a resin soluble or dispersible in the solvent used in the coating agent, a dispersant soluble or dispersible in the solvent, a surfactant, a softener, a stabilizer, a film-forming agent, a thickener, etc.

[0194] Among the above, it is preferable to contain a resin that is soluble or dispersible in the solvent used in the coating agent. This improves the coatability and film-forming properties of the coating agent. Examples of such resins include alkyd resins, melamine resins, acrylic resins, urethane resins, polyester resins, phenolic resins, amino resins, fluororesins, epoxy resins, and isocyanate resins.

[0195] It is also preferable to include a dispersant that is soluble or dispersible in the solvent used in the coating agent. This improves the dispersibility of the polyvalent metal compound. Anionic surfactants or nonionic surfactants can be used as the dispersant. Examples of such surfactants include (poly)carboxylates, alkyl sulfates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, alkyl phosphates, aromatic phosphate esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, alkyl allyl sulfates, polyoxyethylene alkyl phosphate esters, sorbitan alkyl esters, glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, polyoxyethylene sorbitol fatty acid esters, polyoxy fatty acid esters, and polyoxyethylene alkylamines. These surfactants may be used alone or in combination.

[0196] When an additive is contained in a coating agent containing a polyvalent metal compound (B) as a main component, the mass ratio of the polyvalent metal compound to the additive (polyvalent metal compound:additive) is preferably within a range of 30:70 to 99:1, and more preferably within a range of 50:50 to 98:2.

[0197] Examples of solvents used in coating agents containing a polyvalent metal compound (B) as a main component include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of coatability, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of manufacturability, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[0198] When a coating agent containing a polycarboxylic acid polymer (A) and a polyvalent metal compound (B) is applied and dried to form a polycarboxylic acid polyvalent metal salt film, the polycarboxylic acid polyvalent metal salt film can be formed by mixing the polycarboxylic acid polymer (A), the polyvalent metal compound (B), a resin or dispersant soluble or dispersible in water or an alcohol as a solvent, and additives as needed, and applying and drying the resulting coating agent by a known coating method. Examples of coating methods include casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metaling bar coating, chamber doctor combined coating, and curtain coating.

[0199] The thickness of the oxygen barrier film 130 is set depending on the required oxygen barrier properties and may be, for example, 0.05 to 5 μm. The thickness of the oxygen barrier film 130 is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.5 μm. If the thickness of the oxygen barrier film 130 is 0.05 μm or more, sufficient oxygen barrier properties are likely to be obtained. If the thickness of the oxygen barrier film 130 is 1 μm or less, it is easy to form a uniform coated surface, and drying load and production costs can be reduced.

[0200] In the oxygen barrier coating 130, a gas barrier film having the organic-inorganic composite coating or the polyvalent metal salt coating of polycarboxylic acid exhibits excellent oxygen barrier properties even when subjected to boiling or retort sterilization, and when laminated with a sealant film, has sufficient adhesion strength and sealing strength to be used as a packaging material for boiling or retort treatment.Furthermore, it has advantages such as transparency not found in metal foils or metal vapor-deposited films, excellent bending resistance and stretching resistance, and no risk of generating harmful substances such as dioxins.

[0201] [Method for manufacturing gas barrier film] The gas barrier film 101 can be produced by forming either an underlayer 140 or an inorganic oxide layer 150, or both the underlayer 140 and the inorganic oxide layer 150, on the first surface 21 of the resin substrate 120, and then forming the oxygen barrier coating 130 on the underlayer 140 or the inorganic oxide layer 150. The method for producing the gas barrier film 101 of the present disclosure includes, for example, a selection step, an underlayer forming step, an inorganic oxide layer forming step, and an oxygen barrier coating forming step.

[0202] In the sorting process, for example, the number of protrusions on the surface with a Feret diameter of 8 μm or more is 20 / mm 2 The following steps include a step of selecting a raw resin substrate as the resin substrate 120. The number of protrusions on the surface of the raw resin substrate is measured using the same method as the method for measuring the number of protrusions on the first surface 21 of the resin substrate 120 described above. The resin substrate 120 may be a commercially available product, or may be one manufactured by a known method. It's fine.

[0203] An example of the underlayer formation step is a step of applying a coating agent to at least the first surface 21 of the resin substrate 120 by wet coating to form a coating film, and then drying the coating film (removing the solvent) to form the underlayer 140. Known wet coating methods can be used to apply the coating agent. Examples of wet coating methods include roll coating, gravure coating, reverse coating, die coating, screen printing, and spray coating. Known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used to dry the coating film made of the coating agent. Drying conditions include, for example, 90°C for 10 seconds.

[0204] The inorganic oxide layer forming process may include, for example, a process of forming an inorganic oxide layer 150 on the first surface 21 of the resin substrate 120 or on the underlayer 140 by the above-mentioned vacuum deposition method, sputtering method, ion plating method, plasma vapor deposition (CVD), or the like.

[0205] An example of the oxygen barrier film formation process is a process in which a coating agent is applied to the underlayer 140 or the inorganic oxide layer 150 by wet coating to form a coating film, and the coating film is then dried (to remove the solvent) to form the oxygen barrier film 130. Known wet coating methods can be used to apply the coating agent. Examples of wet coating methods include roll coating, gravure coating, reverse coating, die coating, screen printing, and spray coating. Known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used to dry the coating film made of the coating agent. Drying conditions include, for example, 90°C for 10 seconds. The oxygen barrier film 130 can be formed by a single application and drying, or by repeated application and drying of the same or different coating agents multiple times.

[0206] When the manufacturing method of the gas barrier film 101 of the present disclosure includes a selection step, the number of protrusions having a Feret's diameter of 8 μm or more on the surface is 20 / mm 2 The following resin substrate 120 can be efficiently applied. Therefore, by including the selection step, a gas barrier film with improved oxygen barrier properties can be efficiently produced. In addition, by including the selection step, a gas barrier film 101 with good printability can be efficiently produced.

[0207] The gas barrier film 101 of the present disclosure may further include a printing layer, a protective layer, a light-shielding layer, an adhesive layer, a heat-sealable heat-fusible layer, other functional layers, etc., as necessary. When the gas barrier film 101 of the present disclosure includes a heat-sealable heat-fusible layer, the heat-fusible layer is disposed on at least one outermost layer of the gas barrier film 101. By including the heat-fusible layer in the gas barrier film 101, the gas barrier film 101 becomes sealable by heat sealing (for example, a package or a lid). The heat-fusible layer can be laminated, for example, to a laminate obtained by forming the underlayer 140, inorganic oxide layer 150, and oxygen barrier coating 130 of the present embodiment on one or both sides of the resin substrate 120 using a known adhesive such as a polyurethane-based, polyester-based, or polyether-based adhesive by a known dry lamination method, extrusion lamination method, or the like.

[0208] <Action and effect> In the gas barrier film 101 of the present disclosure, the resin layer forming the first surface 21 is made of a polyolefin copolymer resin, and the first surface has 20 protrusions per mm 2 with a Feret diameter of 8 μm or more as measured by the above-mentioned measurement method. 2 On the first surface 21 of the resin substrate 120 described below, either a base layer 140 or an inorganic oxide layer 150, or both the base layer 140 and the inorganic oxide layer 150, are laminated, and further laminated with an oxygen barrier coating 130. The gas barrier film 101 of the present disclosure has a surface layer 23 made of a polyolefin copolymer resin, and has protrusions with a Feret's diameter of 8 μm or more at a density of 20 / mm 2Because the oxygen barrier coating 130 is formed on the resin substrate 120 described below via either the underlayer 140 or the inorganic oxide layer 150, or both, film defects caused by large protrusions on the substrate surface are less likely to occur, improving oxygen barrier properties and ensuring good adhesion of the oxygen barrier coating 130. In addition, the gas barrier film 101 of the present disclosure does not require the underlayer 140, inorganic oxide layer 150, or oxygen barrier coating 130 to be unduly thick, thereby improving productivity and reducing material usage. Therefore, by using the gas barrier film 101 of the present disclosure as a packaging material, it is possible to achieve sufficient lamination strength for packaging materials and improve the quality retention of contents at low cost. [Example]

[0209] Hereinafter, the embodiments of the present disclosure will be described in more detail with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0210] The materials used in the following examples are listed below. [Materials used] <Resin substrate> α1: Biaxially oriented polypropylene film (product name: M-1, thickness 20 μm, one-sided corona treatment, manufactured by Mitsui Chemicals Tohcello Co., Ltd.). α2: Biaxially oriented polypropylene film (product name: ME-1, thickness 20 μm, one-sided corona treatment, manufactured by Mitsui Chemicals Tohcello Co., Ltd.). α3: Biaxially oriented polypropylene film (product name: TS18TI-TPN, thickness 18 μm, one side corona treated, manufactured by Max Specialty Films Limited). α4: Biaxially oriented polypropylene film (product name: P2111, thickness 20 μm, one side corona treated, manufactured by Toyobo Co., Ltd.). α5: Biaxially oriented polypropylene film (product name: P2171, thickness 20 μm, one-sided corona treatment, manufactured by Toyobo Co., Ltd.). α6: Biaxially oriented polypropylene film (product name: P2102, thickness 20 μm, one-side corona treatment, manufactured by Toyobo Co., Ltd.). α7: Biaxially oriented polypropylene film (product name: P2161, thickness 20 μm, one side corona treated, manufactured by Toyobo Co., Ltd.). α8: Biaxially oriented polypropylene film (product name: VPH2011, thickness 20 μm, one side corona treated, average particle size of AB agent on the corona treated side 2 μm, manufactured by AJPlast). α9: Biaxially oriented polypropylene film (product name: VPH2011, thickness 20 μm, one side corona treated, average particle size of AB agent on the corona treated side 4 μm, manufactured by AJPlast). α10: Biaxially oriented polypropylene film (product name: PB210J, thickness 20 μm, one side corona treated, manufactured by Futamura Chemical Co., Ltd.). α11: Polyethylene terephthalate film (product name: P60, thickness 12 μm, one-sided corona treatment, manufactured by Toray Industries, Inc.). α12: Polyethylene terephthalate film (product name: E5102, thickness 12 μm, one-sided corona treatment, manufactured by Toyobo Co., Ltd.). α13: Polyethylene film (product name: HD, thickness 40 μm, one side corona treated, manufactured by Tamapoly Co., Ltd.). α14: Polyethylene film (product name: HS31, thickness 30 μm, one side corona treated, manufactured by Tamapoly Co., Ltd.). α15: Linear low-density polyethylene film (product name: UB-3, thickness 40 μm, one-sided corona treatment, manufactured by Tamapoly Co., Ltd.). α16: Polyethylene film (product name: PE3K-H, thickness 25 μm, one side corona treated, manufactured by Futamura Chemical Co., Ltd.). α17: Polyethylene film (product name: PE3M, thickness 25 μm, one side corona treated, manufactured by Futamura Chemical Co., Ltd.). α18: Linear low-density polyethylene film (product name: LL-XHT, thickness 25 μm, one-sided corona treatment, manufactured by Futamura Chemical Co., Ltd.). α19: Linear low-density polyethylene film (product name: LL-RP2, thickness 25 μm, one-sided corona treatment, manufactured by Futamura Chemical Co., Ltd.). α20: Polyethylene film (thickness 25 μm, one side corona treated, manufactured by WINPAK Limited).

[0211] <Production Example 1> Using Acrydic CL-1000 (manufactured by DIC Corporation) as the acrylic polyol and TDI type curing agent Coronate 2030 (manufactured by Tosoh Corporation) as the isocyanate compound, the acrylic polyol and isocyanate compound were mixed in a solids weight ratio of 6:4, and a dilution solvent (ethyl acetate) was used to prepare a mixed liquid (solids content: 2% by mass) for forming the undercoat layer.

[0212] <Production Example 2> 20 parts by mass of an aqueous solution of polyacrylic acid (Aron A-10H, manufactured by Toagosei Co., Ltd., solids concentration 25% by mass) with a number average molecular weight of 200,000 was diluted with 58.9 parts by mass of distilled water. 0.44 parts by mass of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich Co., Ltd.) was then added and stirred to form a uniform solution, preparing a coating agent whose main component is a polycarboxylic acid polymer.

[0213] <Production Example 3> A coating agent containing a polyvalent metal compound as the main component was prepared by mixing 100 parts by mass of an aqueous dispersion of zinc oxide particles (ZE143 manufactured by Sumitomo Osaka Cement) and 2 parts by mass of a curing agent Liofol HAERTER UR 5889-21 (manufactured by Henkel).

[0214] <Production Example 4> An aqueous solution of polyvinyl alcohol resin (PVA, trade name: Poval PVA-105, manufactured by Kuraray Co., Ltd., polyvinyl alcohol with a saponification degree of 98-99% and a polymerization degree of 500) was dissolved, and an aqueous solution of tetraethoxysilane (TEOS) and γ-glycidoxypropyltrimethoxysilane (GPTMS, trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were each hydrolyzed with 0.02 mol / L hydrochloric acid. The aqueous solutions were mixed so that the weight ratio of PVA:TEOS:GPTMS was 40:50:10 before hydrolysis. A dilution solvent was then added to the mixed solution so that the mass ratio of the solvent components was 90:10 (water:isopropyl alcohol), to prepare a coating agent (5% by mass) for forming an organic-inorganic composite film.

[0215] [Measurement of black area ratio of resin substrate] The black area ratio was determined for the corona-treated surface of each of the resin substrates α1 to α12 under the image acquisition and image analysis conditions described above. The results are shown in Table 1. The black area ratio was measured using an optical microscope OLS-4000 manufactured by Olympus Corporation, equipped with a 10x objective lens (MPFLN10), and Scion ImageJ from Scion Corporation as image analysis software.

[0216] [Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-4] The corona-treated surface of the resin substrate listed in Table 1 was coated with the mixture for forming the underlayer prepared in Production Example 1 using a gravure printer to form a coating film, and the film was dried in a 100 ° C. oven for 10 seconds to form a 0.1 μm thick underlayer. Next, on the formed underlayer, a coating agent mainly composed of a polycarboxylic acid polymer prepared in Production Example 2 was coated using a gravure printer to form a coating film, and the film was dried in a 100 ° C. oven for 10 seconds to form a 0.2 μm thick polycarboxylic acid polymer film. Further, on the polycarboxylic acid polymer film, a coating agent mainly composed of a polyvalent metal compound prepared in Production Example 3 was coated using a gravure printer to form a coating film, and the film was dried in a 100 ° C. oven for 10 seconds to form a 0.2 μm thick polyvalent metal compound film, forming an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid film, and the gas barrier films of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-4 were obtained.

[0217] <Printability evaluation> Black ink (product name: N920LPGT, manufactured by Toyo Ink Co., Ltd.) was printed on the oxygen barrier coating of each gas barrier film using a gravure printer at a dot density of 5% to 50% (in 5% increments). The ink viscosity was 14 seconds (Zahn cup #3, 25°C). The printing speed was 150 m / min, and the drying temperature was 50°C. The printed surface was observed under an optical microscope, and the number of missing dots was counted. The evaluation was as follows: ○ if there were fewer than 5 missing dots in a 6 mm square area; △ if there were 5 to 20 missing dots; × if there were 21 or more missing dots. The evaluation results are shown in Table 1.

[0218] "Missing dots" refers to a state in which ink does not adhere well to the film substrate, resulting in partial dot (halftone dot) transfer. The fewer missing dots there are, even at low halftone dot densities, the better the printability of the highlights.

[0219] <Evaluation of oxygen barrier property and water vapor barrier property after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing, consisting of gas barrier film / adhesive / CPP. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Advanced Films. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for three days. The oxygen barrier coating of the gas barrier film was positioned so that it faced the adhesive.

[0220] An A5-sized four-side sealed pouch was made from the obtained gas barrier laminate film, filled with 150 ml of tap water, and subjected to heat sterilization treatment (retort treatment) in hot water at 120°C for 30 minutes.

[0221] The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The results are shown in Table 1.

[0222] [Table 1]

[0223] From the results shown in Table 1, the gas barrier films of Examples 1-1 to 1-8 had a black area ratio of 0.15% or less and an oxygen permeability of 2 cm or less in an atmosphere of 30°C and a relative humidity of 70%. 3 / (m 2 Good oxygen barrier properties were obtained at temperatures below 1000 kJ / day atm.

[0224] On the other hand, the gas barrier films of Comparative Examples 1-1 to 1-4 have a black area ratio of 0.15% or more and an oxygen permeability of 2 cm 3 / (m 2 The black area ratio exceeded 0.15%, which increased the oxygen permeability, and as a result, good oxygen barrier properties were not obtained compared to Examples 1-1 to 1-8.

[0225] From the results shown in Table 1, the gas barrier films of Examples 1-1 to 1-8 were rated "good" for printability at a dot density of 30% or more.

[0226] On the other hand, the gas barrier films of Comparative Examples 1-1 to 1-4 were rated "poor" for printability at a dot density of 30%.

[0227] Thus, it was found that printability was good when the black area ratio was 0.15% or less.

[0228] [Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4] The corona-treated surface of the resin substrate listed in Table 2 was coated with the mixture for forming the undercoat layer prepared in Production Example 1 using a gravure printer to form a coating film, and the coated film was then dried in a 100°C oven for 10 seconds to form a 0.1 μm-thick undercoat layer. Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide was evaporated using an electron beam heating vacuum deposition device to form a 30 nm-thick inorganic oxide layer composed of silicon oxide on the undercoat layer. The organic-inorganic composite coating agent prepared in Production Example 4 was then coated on the inorganic oxide layer using a gravure printer to form a coating film, and the film was then dried in a 100°C oven for 10 seconds to form a 0.3 μm-thick oxygen barrier coating composed of an organic-inorganic composite coating, resulting in the gas barrier films of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4.

[0229] [Example 2-7] A gas barrier film of Example 2-7 was obtained in the same manner as in Example 2-3, except that an inorganic oxide layer was formed directly on the corona-treated surface of the resin substrate α8 without providing an undercoat layer.

[0230] <Printability evaluation> Black ink (product name: N920LPGT, manufactured by Toyo Ink Co., Ltd.) was printed on the oxygen barrier coating of each gas barrier film using a gravure printer at a halftone dot density of 5% to 50% (in 5% increments). The ink viscosity was 14 seconds (Zahn cup #3, 25°C). The printing speed was 150 m / min, and the drying temperature was 50°C. The printed surface was observed under an optical microscope, and the number of missing dots was counted. The evaluation was as follows: ○ if there were fewer than 5 missing dots in a 6 mm square area; △ if there were 5 to 20 missing dots; × if there were 21 or more missing dots. The evaluation results are shown in Table 2.

[0231] "Missing dots" refers to a state in which ink does not adhere well to the film substrate, resulting in partial dot (halftone dot) transfer. The fewer missing dots there are, even at low halftone dot densities, the better the printability of the highlights.

[0232] <Evaluation of oxygen barrier property and water vapor barrier property after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing, consisting of gas barrier film / adhesive / CPP. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Advanced Films. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for three days. The oxygen barrier coating of the gas barrier film was positioned so that it faced the adhesive.

[0233] An A5-sized four-side sealed pouch was made from the obtained gas barrier laminate film, filled with 150 ml of tap water, and subjected to heat sterilization treatment (retort treatment) in hot water at 120°C for 30 minutes.

[0234] The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The results are shown in Table 2.

[0235] [Table 2]

[0236] From the results shown in Table 2, the gas barrier films of Examples 2-1 to 2-7 had a black area ratio of 0.15% or less and an oxygen permeability of 3 cm or less in an atmosphere of 30°C and 70% relative humidity. 3 / (m 2Good oxygen barrier properties were obtained at temperatures below 1000 kJ / day atm.

[0237] On the other hand, the gas barrier films of Comparative Examples 2-1 to 2-4 have a black area ratio of 0.15% or more and an oxygen permeability value of 5 cm 3 / (m 2 The black area ratio exceeded 0.15%, which increased the oxygen permeability, and as a result, good oxygen barrier properties were not obtained compared to Examples 2-1 to 2-7.

[0238] From the results shown in Table 2, the gas barrier films of Examples 2-1 to 2-7 were rated "good" for printability at a dot density of 30% or more.

[0239] On the other hand, the gas barrier films of Comparative Examples 2-1 to 2-4 were rated "X" for printability at a dot density of 30%.

[0240] Thus, it was found that printability was good when the black area ratio was 0.15% or less.

[0241] [Examples 3-1 to 3-7 and Comparative Example 3-1] The mixed solution for forming the underlayer prepared in Production Example 1 was applied to the corona-treated surface of the resin substrate listed in Table 3 using a gravure printing machine to form a coating, and the coating was then dried in an oven at 100°C for 10 seconds to form an underlayer with a thickness of 0.1 μm. Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide was evaporated using a vacuum deposition device using an electron beam heating system to form an inorganic oxide layer made of silicon oxide with a thickness of 30 nm on the underlayer. Next, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 was applied onto the formed inorganic oxide layer using a gravure printing machine to form a coating film, and the film was dried in a 100°C oven for 10 seconds to form a polycarboxylic acid polymer film with a thickness of 0.2 μm. Further, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 was applied onto the polycarboxylic acid polymer film using a gravure printing machine to form a coating film, and the film was dried in a 100°C oven for 10 seconds to form a polyvalent metal compound film with a thickness of 0.2 μm. Thus, an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid film was formed, and the gas barrier films of Examples 3-1 to 3-7 and Comparative Example 3-1 were obtained.

[0242] [Examples 3-8] A gas barrier film of Example 3-8 was obtained in the same manner as in Example 3-4, except that an inorganic oxide layer was formed directly on the corona-treated surface of the resin substrate α8 without providing an undercoat layer.

[0243] <Printability evaluation> Black ink (product name: N920LPGT, manufactured by Toyo Ink Co., Ltd.) was printed on the oxygen barrier coating of each gas barrier film using a gravure printer at a dot density of 5% to 50% (in 5% increments). The ink viscosity was 14 seconds (Zahn cup #3, 25°C). The printing speed was 150 m / min, and the drying temperature was 50°C. The printed surface was observed under an optical microscope, and the number of missing dots was counted. The evaluation was as follows: ○ if there were fewer than 5 missing dots in a 6 mm square area; △ if there were 5 to 20 missing dots; × if there were 21 or more missing dots. The evaluation results are shown in Table 3.

[0244] "Missing dots" refers to a state in which ink does not adhere well to the film substrate, resulting in partial dot (halftone dot) transfer. The fewer missing dots there are, even at low halftone dot densities, the better the printability of the highlights.

[0245] <Evaluation of oxygen barrier property and water vapor barrier property after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing, consisting of gas barrier film / adhesive / CPP. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Advanced Films. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for three days. The oxygen barrier coating of the gas barrier film was positioned so that it faced the adhesive.

[0246] An A5-sized four-side sealed pouch was made from the obtained gas barrier laminate film, filled with 150 ml of tap water, and subjected to heat sterilization treatment (retort treatment) in hot water at 120°C for 30 minutes.

[0247] The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The results are shown in Table 3.

[0248] [Table 3]

[0249] From the results shown in Table 3, the gas barrier films of Examples 3-1 to 3-8 had a black area ratio of 0.15% or less and an oxygen permeability of 2 cm or less in an atmosphere of 30°C and a relative humidity of 70%. 3 / (m 2 Good oxygen barrier properties were obtained at temperatures below 1000 kJ / day atm.

[0250] On the other hand, the gas barrier film of Comparative Example 3-1 had a black area ratio of 0.15% or more and an oxygen permeability of 4.7 cm 3 / (m 2 ·day·atm) and Examples 3-1 to 3-8 In comparison, good oxygen barrier properties were not obtained.

[0251] From the results shown in Table 3, the gas barrier films of Examples 3-1 to 3-8 were rated "good" for printability at a dot density of 30% or more.

[0252] On the other hand, the gas barrier film of Comparative Example 3-1 was rated "X" for printability at a dot density of 30%.

[0253] Thus, it was found that printability was good when the black area ratio was 0.15% or less.

[0254] [Examples 4-1 to 4-5 and Comparative Example 4-1] The mixed solution for forming the underlayer prepared in Production Example 1 was applied to the corona-treated surface of the resin substrate listed in Table 4 using a gravure printing machine to form a coating, and the coating was dried in an oven at 100°C for 10 seconds to form an underlayer with a thickness of 0.1 μm. Next, metallic aluminum was evaporated using a vacuum deposition device using an electron beam heating system, and oxygen gas was introduced thereto to form an inorganic oxide layer made of aluminum oxide with a thickness of 20 nm on the underlayer. Next, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 was applied onto the formed inorganic oxide layer using a gravure printing machine to form a coating film, and the film was dried in a 100°C oven for 10 seconds to form a polycarboxylic acid polymer film with a thickness of 0.2 μm. Further, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 was applied onto the polycarboxylic acid polymer film using a gravure printing machine to form a coating film, and the film was dried in a 100°C oven for 10 seconds to form a polyvalent metal compound film with a thickness of 0.2 μm. Thus, an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid film was formed, and the gas barrier films of Examples 4-1 to 4-5 and Comparative Example 4-1 were obtained.

[0255] [Examples 4-6] A gas barrier film of Example 4-6 was obtained in the same manner as in Example 4-2, except that an inorganic oxide layer was formed directly on the corona-treated surface of the resin substrate α8 without providing an undercoat layer.

[0256] <Printability evaluation> Black ink (product name: N920LPGT, manufactured by Toyo Ink Co., Ltd.) was printed on the oxygen barrier coating of each gas barrier film using a gravure printer at a dot density of 5% to 50% (in 5% increments). The ink viscosity was 14 seconds (Zahn cup #3, 25°C). The printing speed was 150 m / min, and the drying temperature was 50°C. The printed surface was observed under an optical microscope, and the number of missing dots was counted. The evaluation was as follows: ○ if there were fewer than 5 missing dots in a 6 mm square area; △ if there were 5 to 20 missing dots; × if there were 21 or more missing dots. The evaluation results are shown in Table 4.

[0257] "Missing dots" refers to a state in which ink does not adhere well to the film substrate, resulting in partial dot (halftone dot) transfer. The fewer missing dots there are, even at low halftone dot densities, the better the printability of the highlights.

[0258] <Evaluation of oxygen barrier property and water vapor barrier property after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing, consisting of gas barrier film / adhesive / CPP. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Advanced Films. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for three days. The oxygen barrier coating of the gas barrier film was positioned so that it faced the adhesive.

[0259] An A5-sized four-side sealed pouch was made from the obtained gas barrier laminate film, filled with 150 ml of tap water, and subjected to heat sterilization treatment (retort treatment) in hot water at 120°C for 30 minutes.

[0260] The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The results are shown in Table 4.

[0261] [Table 4]

[0262] From the results shown in Table 4, the gas barrier films of Examples 4-1 to 4-6 had a black area ratio of 0.15% or less and an oxygen permeability of 1 cm or less in an atmosphere of 30°C and a relative humidity of 70%. 3 / (m 2 On the other hand, the gas barrier film of Comparative Example 4-1 had a black area ratio of 0.15% or more and an oxygen permeability of 1.5 cm 3 / (m 2 ·day·atm), no good oxygen barrier properties were obtained compared to Examples 4-1 to 4-6.

[0263] From the results shown in Table 4, the gas barrier films of Examples 4-1 to 4-6 were rated "good" for printability at a dot density of 30% or more.

[0264] On the other hand, the gas barrier film of Comparative Example 4-1 was rated "X" for printability at a dot density of 30%.

[0265] Thus, it was found that printability was good when the black area ratio was 0.15% or less.

[0266] [Examples 5-1 to 5-5 and Comparative Examples 5-1 to 5-3] The corona-treated surface of the resin substrate listed in Table 5 was coated with the mixture for forming the undercoat layer prepared in Production Example 1 using a gravure printer to form a coating film, and the film was then dried in a 60°C oven for 10 seconds to form a 0.1 μm-thick undercoat layer. Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide was evaporated using an electron beam heating vacuum deposition device to form a 30 nm-thick inorganic oxide layer composed of silicon oxide on the undercoat layer. The organic-inorganic composite coating agent prepared in Production Example 4 was then coated on the inorganic oxide layer using a gravure printer to form a coating film, and the film was then dried in a 60°C oven for 10 seconds to form a 0.3 μm-thick oxygen barrier coating composed of an organic-inorganic composite coating, resulting in the gas barrier films of Examples 5-1 to 5-5 and Comparative Examples 5-1 to 5-3.

[0267] [Examples 5-6] A gas barrier film of Example 5-6 was obtained in the same manner as in Example 5-2, except that an inorganic oxide layer was formed directly on the corona-treated surface of the resin substrate α14 without providing an undercoat layer.

[0268] [Examples 5-7 to 5-11 and Comparative Examples 5-4 to 5-6] The mixed solution for forming the underlayer prepared in Production Example 1 was applied to the corona-treated surface of the resin substrate listed in Table 5 using a gravure printing machine to form a coating, and the coating was dried in a 60°C oven for 10 seconds to form a 0.1 μm thick underlayer. Next, metallic aluminum was evaporated using a vacuum deposition device using an electron beam heating system, and oxygen gas was introduced thereto to form a 20 nm thick inorganic oxide layer made of aluminum oxide on the underlayer. Next, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 was applied onto the formed inorganic oxide layer using a gravure printing machine to form a coating film, and the film was dried in a 60°C oven for 10 seconds to form a polycarboxylic acid polymer film with a thickness of 0.2 μm.Furthermore, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 was applied onto the polycarboxylic acid polymer film using a gravure printing machine to form a coating film, and the film was dried in a 50°C oven for 10 seconds to form a polyvalent metal compound film with a thickness of 0.2 μm.This formed an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid film, and the gas barrier films of Examples 5-7 to 5-11 and Comparative Examples 5-4 to 5-6 were obtained.

[0269] [Examples 5-12] A gas barrier film of Example 5-12 was obtained in the same manner as in Example 5-8, except that an inorganic oxide layer was formed directly on the corona-treated surface of the resin substrate α14 without providing an undercoat layer.

[0270] [Example 5-13] The gas barrier film of Example 5-13 was obtained in the same manner as in Example 5-8, except that a polyvalent metal compound film was formed on the undercoat layer formed on the corona-treated surface of the resin substrate α14 without providing an inorganic oxide layer.

[0271] <Evaluation of oxygen barrier property and water vapor barrier property before and after boiling treatment> Each gas barrier film was bonded to LLDPE (polyethylene film) using an adhesive to produce a gas barrier laminate film for boiling treatment, consisting of gas barrier film / adhesive / LLDPE. The adhesive used was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The LLDPE was a polyethylene film, TUX MC-S (60 μm), manufactured by Mitsui Chemicals Tohcello. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for three days. The oxygen barrier coating of the gas barrier film was positioned so that it faced the adhesive.

[0272] An A5-sized four-side sealed pouch was made from the obtained gas barrier laminate film, filled with 150 ml of tap water, and subjected to heat sterilization treatment (boiling treatment) in hot water at 90°C for 30 minutes.

[0273] The gas barrier laminate film before and after the boiling treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The results are shown in Table 5.

[0274] [Table 5]

[0275] From the results shown in Table 5, the gas barrier films of Examples 5-1 to 5-6 had a black area ratio of 0.15% or less, and an oxygen permeability of 2 cm or less before boiling in an atmosphere of 30°C and a relative humidity of 70%. 3 / (m2 ·day·atm) or less, 3cm after boiling 3 / (m 2 ·day·atm) or less, and good oxygen barrier properties were obtained.

[0276] The gas barrier films of Examples 5-7 to 5-13 had a black area ratio of 0.15% or less, and the oxygen permeability values ​​in an atmosphere of 30°C and 70% relative humidity were 1 cm or less before and after boiling. 3 / (m 2 ·day·atm) or less, and good oxygen barrier properties were obtained.

[0277] On the other hand, the gas barrier films of Comparative Examples 5-1 to 5-3 have a black area ratio of 0.15% or more and an oxygen permeability of 2 cm before boiling. 3 / (m 2 ·day·atm) or more, after boiling 3cm 3 / (m 2 ·day·atm) or more, and good oxygen barrier properties were not obtained.

[0278] The gas barrier films of Comparative Examples 5-4 to 5-6 had a black area ratio of 0.15% or more and an oxygen permeability of 1 cm or less before and after boiling. 3 / (m 2 ·day·atm) or more, and good oxygen barrier properties were not obtained.

[0279] [Examples 6-1 to 6-4 and Comparative Examples 6-1 to 6-5] In Examples 6-1 to 6-4 and Comparative Examples 6-1 to 6-5, the influence of the production lot of the resin substrate was examined.

[0280] The corona-treated surface of the resin substrate shown in Table 6A was coated with the mixture for forming the undercoat layer prepared in Production Example 1 using a gravure printer to form a coating film, and then dried in a 100 ° C. oven for 10 seconds to form a 0.1 μm thick undercoat layer. Next, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 was applied to the formed undercoat layer using a gravure printer to form a coating film, and then dried in a 100 ° C. oven for 10 seconds to form a 0.2 μm thick polycarboxylic acid polymer film. Further, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 was applied to the polycarboxylic acid polymer film using a gravure printer to form a coating film, and then dried in a 100 ° C. oven for 10 seconds to form a 0.2 μm thick polyvalent metal compound film, forming an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid. Gas barrier films were obtained in Experimental Examples 6-1 to 6-4 and Comparative Examples 6-1 to 6-5.

[0281] [Examples 6-5 to 6-8 and Comparative Examples 6-6 to 6-10] The corona-treated surface of the resin substrate shown in Table 6B was coated with the mixture for forming the primer layer prepared in Production Example 1 using a gravure printer to form a coating film, and the film was then dried in a 100°C oven for 10 seconds to form a 0.1 μm-thick primer layer. Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide was evaporated using an electron beam heating vacuum deposition device to form a 30 nm-thick inorganic oxide layer composed of silicon oxide on the primer layer. The organic-inorganic composite coating agent prepared in Production Example 4 was then coated on the inorganic oxide layer using a gravure printer to form a coating film, and the film was then dried in a 100°C oven for 10 seconds to form a 0.3 μm-thick oxygen barrier coating composed of an organic-inorganic composite coating, resulting in the gas barrier films of Examples 6-5 to 6-8 and Comparative Examples 6-6 to 6-10.

[0282] The black area ratio, oxygen permeability and printability of the resin substrate were evaluated in the same manner as in Examples 1-1 to 1-8. The measurement results are shown in Tables 6A and 6B.

[0283] [Table 6A]

[0284] [Table 6B] First, the resin substrates used in Examples 6-1 to 6-4 and Comparative Example 6-1 were the same in material, product number, manufacturer, and thickness, but were from different production lots. Similarly, the resin substrates used in Examples 6-5 to 6-8 and Comparative Example 6-6 were the same in material, product number, manufacturer, and thickness, but were from different production lots. However, the black area ratios of the resin substrates measured by the above-mentioned method varied for each production lot. That is, from the measurement results of the black area ratios shown in Tables 6A and 6B, it was confirmed that the black area ratios measured by the above-mentioned method were not specific to the type of resin substrate (α8 or α9), but varied depending on the production lot.

[0285] Next, from the results shown in Tables 6A and 6B, the gas barrier films according to Examples 6-1 to 6-4 and 6-5 to 6-8 (in which the black area ratio of the resin substrate was 0.15% or less) exhibited good oxygen barrier properties in an atmosphere of 30°C and relative humidity of 70%, and were evaluated as "good" for printability at a dot density of 30% or more. In contrast, the gas barrier film according to Comparative Example 6-1 had a black area ratio of the resin substrate exceeding 0.15%, and thus exhibited higher oxygen permeability and worse printability than the gas barrier films according to Examples 6-1 to 6-4 with the same configuration. Similarly, the gas barrier film according to Comparative Example 6-6 also had a black area ratio of the resin substrate exceeding 0.15%, and thus exhibited higher oxygen permeability and worse printability than the gas barrier films according to Examples 6-5 to 6-8 with the same configuration.

[0286] These results demonstrate that, even when gas barrier films of the same configuration are constructed using the same type of resin substrate, differences in the performance of the gas barrier film occur depending on the production lot of the resin substrate; however, if the black area ratio of the resin substrate is 0.15% or less, the effects of the production lot of the resin substrate can be reduced.

[0287] Hereinafter, the second embodiment of the present disclosure will be described in more detail with reference to examples and comparative examples. However, the present disclosure is not limited to the following examples. The materials used in each example are shown below.

[0288] [Materials used] <Resin substrate> β1: Biaxially oriented polypropylene film (product name: ME-1, thickness 20 μm, surface layer made of polyolefin copolymer resin, manufactured by Mitsui Chemicals Tocello Co., Ltd.). β2: Biaxially oriented polypropylene film (product name: P2111, thickness 20 μm, surface layer is polyolefin copolymer resin, manufactured by Toyobo Co., Ltd.). β3: Biaxially oriented polypropylene film (product name: VPH2011, thickness 20 μm, surface layer is polyolefin copolymer resin, contains AB agent with average particle size of 2 μm, manufactured by AJPlast). β4: Biaxially oriented polypropylene film (product name: VPH2011, thickness 20 μm, surface layer is polyolefin copolymer resin, contains AB agent with average particle size of 4 μm, manufactured by AJPlast). β5: Biaxially oriented polypropylene film (product name: TS19TIMCP, thickness 19 μm, surface layer made of polyolefin copolymer resin, manufactured by Max Speciality Films Limited). β6: Biaxially oriented polypropylene film (product name: TS18TIV, thickness 18 μm, surface layer is polyolefin copolymer resin, manufactured by Max Speciality Films Limited). β7: Biaxially oriented polypropylene film (product name: TS18TI-TPN, thickness 18 μm, surface layer is polypropylene homopolymer, manufactured by Max Speciality Films Limited). β8: Biaxially oriented polypropylene film (product name: M-1, thickness 20 μm, surface layer is polypropylene homopolymer, manufactured by Mitsui Chemicals Tocello Co., Ltd.).

[0289] [Measurement of the number of protrusions on the surface of a resin substrate] The number of protrusions having a Feret's diameter of 8 μm or more was counted for each of the surfaces (first surfaces) of the resin substrates β1 to β8 on which the oxygen barrier coating was to be formed, according to the measurement conditions described above. The results are shown in Tables 7 to 10.

[0290] [Examples 7-1 to 7-3 and Comparative Examples 7-1 to 7-5] The first surface of each resin substrate listed in Table 7 was coated with the mixture for forming the underlayer prepared in Production Example 1 using a gravure printer to form a coating film, which was then dried in a 100°C oven for 10 seconds to form a 0.1 μm-thick underlayer. Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide was evaporated using an electron beam heating vacuum deposition device to form a 30 nm-thick inorganic oxide layer composed of silicon oxide on the underlayer. Next, the coating agent for forming the organic-inorganic composite coating prepared in Production Example 4 was coated on the formed inorganic oxide layer using a gravure printer to form a coating film, which was then dried in a 100°C oven for 10 seconds to form a 0.3 μm-thick oxygen barrier coating composed of an organic-inorganic composite coating, resulting in the gas barrier films of Examples 7-1 to 7-3 and Comparative Examples 7-1 to 7-5.

[0291] [Example 7-4] A gas barrier film of Example 7-4 was obtained in the same manner as in Example 7-3, except that an inorganic oxide layer was formed directly on the first surface of the resin substrate β3 without providing an undercoat layer.

[0292] <Oxygen barrier property, water vapor barrier property, and laminate strength evaluation after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Film Processing Co., Ltd. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for 3 days. The oxygen barrier coating of the gas barrier film was positioned facing the adhesive. A5-sized, four-sided sealed pouches were made using the resulting gas barrier laminate film. They were filled with 200 ml of tap water and subjected to heat sterilization (retort processing) in hot water at 120°C for 30 minutes. The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 ·day)) were measured. The measurement results are shown in Table 7. After retort treatment, 15 mm wide strip test pieces were cut out of the gas barrier laminate film, and the lamination strength between the gas barrier film and the CPP film was measured using a Tensilon RTC-1250 universal testing machine, peeling at a peel speed of 300 m / min in a T-shape and at a 180° peel angle. The measurement results are shown in Table 7.

[0293] [Table 7]

[0294] From the results shown in Table 7, it is clear that the first surface of the resin substrate is a polyolefin copolymer resin, and the number of protrusions of 8 μm or more in Feret's diameter on the first surface of the resin substrate is 20 / mm 2The gas barrier films of Examples 7-1 to 7-4 below have an oxygen permeability of 3 cm under an atmosphere of 30°C and 70% RH. 3 / (m 2 ·day·atm) or less, and the water vapor permeability value is 1g / (m 2 On the other hand, the number of protrusions on the first surface of the resin substrate with a Feret's diameter of 8 μm or more was 20 / mm 2 The gas barrier films of Comparative Examples 7-1 to 7-3, which have an oxygen permeability value exceeding 3 cm 3 / (m 2 ·day·atm) and the water vapor permeability is 1g / (m 2 The oxygen barrier property and water vapor barrier property were inferior.

[0295] The results shown in Table 7 indicate that Comparative Examples 7-4 and 7-5, in which the first surface of the resin substrate was a polypropylene homopolymer, had a laminate strength of less than 2 N / 15 mm after retort treatment, which was insufficient. In contrast, Examples 7-1 to 7-4, in which the first surface of the resin substrate was a polyolefin copolymer resin, had a sufficient laminate strength of 2 N / 15 mm or more even after retort treatment. In particular, Example 7-4 exhibited good laminate strength even without a base layer. Furthermore, "substrate break" in Table 7 indicates that the resin substrate broke at a strength of 2 N / 15 mm or more without peeling between the gas barrier film and the CPP film, indicating that the laminate strength was sufficiently high.

[0296] [Examples 8-1 to 8-3 and Comparative Examples 8-1 to 8-3] The mixed solution for forming the underlayer prepared in Production Example 1 was applied to the first surface of the resin substrate listed in Table 8 using a gravure printing machine to form a coating, and the coating was then dried in an oven at 100°C for 10 seconds to form an underlayer with a thickness of 0.1 µm. Next, a mixed material containing two or more of metallic silicon, silicon monoxide, and silicon dioxide was evaporated using a vacuum deposition apparatus using an electron beam heating system to form an inorganic oxide layer made of silicon oxide with a thickness of 30 nm on the underlayer. Next, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 was applied onto the formed inorganic oxide layer using a gravure printing machine to form a coating film, and the film was dried in a 100°C oven for 10 seconds to form a polycarboxylic acid polymer film with a thickness of 0.2 μm. Further, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 was applied onto the polycarboxylic acid polymer film using a gravure printing machine to form a coating film, and the film was dried in a 100°C oven for 10 seconds to form a polyvalent metal compound film with a thickness of 0.2 μm. Thus, an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid was formed, and the gas barrier films of Examples 8-1 to 8-3 and Comparative Examples 8-1 to 8-3 were obtained.

[0297] [Example 8-4] A gas barrier film of Example 8-4 was obtained in the same manner as in Example 8-3, except that an inorganic oxide layer was formed directly on the first surface of the resin substrate β3 without providing an undercoat layer.

[0298] <Oxygen barrier property, water vapor barrier property, and laminate strength evaluation after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing. The adhesive was a two-component adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Advanced Films. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for 3 days. The oxygen barrier coating of the gas barrier film was positioned facing the adhesive. A5-sized, four-sided sealed pouches were made using the resulting gas barrier laminate film. They were filled with 200 ml of tap water and subjected to heat sterilization (retort processing) in hot water at 120°C for 30 minutes. The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 ·day)) was measured. The measurement results are shown in Table 8. After retort treatment, 15 mm wide strip test pieces were cut out of the gas barrier laminate film, and the lamination strength between the gas barrier film and the CPP film was measured using a Tensilon RTC-1250 universal testing machine, peeling at a T-type and 180° peel angle at a peel speed of 300 m / min. The measurement results are shown in Table 8.

[0299] [Table 8]

[0300] From the results shown in Table 8, it is clear that the first surface of the resin substrate is a polyolefin copolymer resin, and the number of protrusions of 8 μm or more in Feret's diameter on the first surface of the resin substrate is 20 / mm 2The gas barrier films of Examples 8-1 to 8-4 below have an oxygen permeability of 2 cm or more under an atmosphere of 30°C and 70% RH. 3 / (m 2 On the other hand, the first surface of the resin substrate showed 20 protrusions per mm with a Feret diameter of 8 μm or more. 2 The gas barrier films of Comparative Examples 8-1 to 8-3, in which the first surface of the resin substrate is a polypropylene homopolymer, have an oxygen permeability of 2 cm or more. 3 / (m 2 ·day·atm), and the oxygen barrier properties were poor.

[0301] From the results shown in Table 8, Comparative Examples 8-2 to 8-3, in which the first surface of the resin substrate was a polypropylene homopolymer, had a laminate strength of less than 2 N / 15 mm after retort treatment, which was insufficient, whereas Examples 8-1 to 8-4, in which the first surface of the resin substrate was a polyolefin copolymer resin, had a sufficient laminate strength of 2 N / 15 mm or more even after retort treatment. In particular, Example 8-4 exhibited good laminate strength even without a base layer.

[0302] [Examples 9-1 to 9-3 and Comparative Examples 9-1 to 9-3] On the first surface of the resin substrate listed in Table 9, a gravure printing machine was used to coat the mixture for forming the underlayer prepared in Production Example 1 to form a coating film, and the film was dried in an oven at 100 ° C. for 10 seconds to form a 0.1 μm thick underlayer. Next, on the formed underlayer, a gravure printing machine was used to coat the coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 to form a coating film, and the film was dried in an oven at 100 ° C. for 10 seconds to form a 0.2 μm thick polycarboxylic acid polymer film, and further, a gravure printing machine was used to coat the coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 on the polycarboxylic acid polymer film to form a coating film, and the film was dried in an oven at 100 ° C. for 10 seconds to form a 0.2 μm thick polyvalent metal compound film, and an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid film was formed, and the gas barrier films of Examples 9-1 to 9-3 and Comparative Examples 9-1 to 9-3 were obtained.

[0303] <Oxygen barrier property, water vapor barrier property, and laminate strength evaluation after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Film Processing Co., Ltd. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for 3 days. The oxygen barrier coating of the gas barrier film was positioned facing the adhesive. A5-sized, four-sided sealed pouches were made using the resulting gas barrier laminate film. They were filled with 200 ml of tap water and subjected to heat sterilization (retort processing) in hot water at 120°C for 30 minutes. The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The test results are shown in Table 9. After retort treatment, 15 mm wide strip test pieces were cut out of the gas barrier laminate film, and the lamination strength between the gas barrier film and the CPP film was measured using a Tensilon RTC-1250 universal testing machine, peeling at a T-shape and 180° angle at a peel speed of 300 m / min. The test results are shown in Table 9.

[0304] [Table 9]

[0305] From the results shown in Table 9, it is clear that the first surface of the resin substrate is a polyolefin copolymer resin, and the number of protrusions of 8 μm or more in Feret's diameter on the first surface of the resin substrate is 20 / mm 2 The gas barrier films of Examples 9-1 to 9-3 below have an oxygen permeability of 2 cm or more under an atmosphere of 30°C and 70% RH. 3 / (m 2 The laminate strength after retort treatment was also sufficient, at 2N / 15mm or more. On the other hand, the number of protrusions on the first surface of the resin substrate with a Feret diameter of 8μm or more was 20 / mm. 2 The gas barrier films of Comparative Examples 9-1 to 9-3, which have an oxygen permeability value exceeding 2 cm 3 / (m 2 ·day·atm), and the oxygen barrier properties were poor.

[0306] [Example 10-1 and Comparative Example 10-1] The mixed solution for forming the underlayer prepared in Production Example 1 was applied to the first surface of the resin substrate listed in Table 10 using a gravure printing machine to form a coating, and the coating was dried in an oven at 100°C for 10 seconds to form an underlayer with a thickness of 0.1 μm. Next, metallic aluminum was evaporated using a vacuum deposition device using an electron beam heating system, and oxygen gas was introduced thereto to form an inorganic oxide layer made of aluminum oxide with a thickness of 20 nm on the underlayer. Next, a coating agent mainly composed of the polycarboxylic acid polymer prepared in Production Example 2 was applied onto the formed inorganic oxide layer using a gravure printing machine to form a coating film, and the film was dried in an oven at 100°C for 10 seconds to form a polycarboxylic acid polymer film with a thickness of 0.2 μm. Further, a coating agent mainly composed of the polyvalent metal compound prepared in Production Example 3 was applied onto the polycarboxylic acid polymer film using a gravure printing machine to form a coating film, and the film was dried in an oven at 100°C for 10 seconds to form a polyvalent metal compound film with a thickness of 0.2 μm. Thus, an oxygen barrier film consisting of a polyvalent metal salt of polycarboxylic acid was formed, and the gas barrier films of Example 10-1 and Comparative Example 10-1 were obtained.

[0307] <Oxygen barrier property, water vapor barrier property, and laminate strength evaluation after retort processing> Each gas barrier film was bonded to a CPP (polypropylene film) using an adhesive to produce a gas barrier laminate film for retort processing. The adhesive was a two-component curing adhesive, Takelac A620 (base) / Takenate A65 (curing agent), manufactured by Mitsui Chemicals Polyurethanes. The CPP was a polypropylene film, Torayfan ZK93KM (60 μm), manufactured by Toray Film Processing Co., Ltd. The films were dry-laminated using a HIRANO TECSEED multi-coater TM-MC and aged at 40°C for 3 days. The oxygen barrier coating of the gas barrier film was positioned facing the adhesive. A5-sized, four-sided sealed pouches were made using the resulting gas barrier laminate film. They were filled with 200 ml of tap water and subjected to heat sterilization (retort processing) in hot water at 120°C for 30 minutes. The gas barrier laminate film after retort treatment was measured for oxygen permeability (cm) under an atmosphere of 30°C and 70% RH using an oxygen permeability measuring device (product name: OXTRAN-2 / 20, manufactured by MOCON). 3 / (m 2 The water vapor permeability (g / (m)) was measured using a water vapor permeability measuring device (product name: PERMATRAN-W-3 / 33, manufactured by MOCON) under an atmosphere of 40°C and 90% RH. 2 The test results are shown in Table 10. After retort treatment, 15 mm wide strips of test specimens were cut out of the gas barrier laminate film, and the lamination strength between the gas barrier film and the CPP film was measured using a Tensilon RTC-1250 universal testing machine, peeling at a T-type and 180° angle at a peel speed of 300 m / min. The test results are shown in Table 10.

[0308] [Table 10]

[0309] From the results shown in Table 10, it is clear that the first surface of the resin substrate is a polyolefin copolymer resin, and the number of protrusions of 8 μm or more in Feret's diameter on the first surface of the resin substrate is 20 / mm 2The gas barrier film of Example 10-1 below has an oxygen permeability of 2 cm under an atmosphere of 30°C and 70% RH. 3 / (m 2 The gas barrier film of Comparative Example 10-1, in which the first surface of the resin substrate was a polypropylene homopolymer, exhibited good oxygen barrier properties of 2 N / 15 mm or less (200 psi / day atm) and had sufficient lamination strength after retort treatment of 2 N / 15 mm or more. On the other hand, the gas barrier film of Comparative Example 10-1, in which the first surface of the resin substrate was a polypropylene homopolymer, did not exhibit sufficient strength, exhibiting lamination strength (T-peel) after retort treatment of less than 2 N / 15 mm. [Industrial Applicability]

[0310] The gas barrier film of the present disclosure stably exhibits excellent gas barrier properties, even after retort treatment. In addition, the surface condition of the substrate film can be easily determined, and the quality can be stabilized even when the oxygen barrier coating is thin, making it possible to reduce raw material costs.

[0311] In addition, the gas barrier film of the present disclosure has good printability, so that printing can be easily and beautifully applied to the surface of the gas barrier film.

[0312] The gas barrier film of the present disclosure can be suitably used, for example, as a packaging material, and can also be suitably used as a packaging material for boiling treatment and retort treatment. By using the gas barrier film of the present disclosure as a packaging material, the quality retention of the contents can be improved.

[0313] The gas barrier film of the present disclosure can also be used for applications other than packaging materials, such as electronic device-related films, solar cell films, various functional films for fuel cells, and substrate films. [Explanation of symbols]

[0314] 1. Gas barrier film 10 Resin substrate 20 Oxygen barrier coating 30 Lower strata 40 Inorganic acid layer

Claims

1. A method for selecting a resin substrate for a gas barrier film, comprising: A method for selecting a resin substrate for a gas barrier film, comprising the steps of: measuring a black area ratio on a surface of a resin substrate raw sheet by the following measurement method; and preparing, as the resin substrate, a resin substrate raw sheet having a black area ratio of 0.15% or less on at least one surface. <Measurement method> An arbitrary 1281 μm square area on one side of the resin substrate is photographed with an optical microscope to obtain a photographed image of 1024 × 1024 pixels, and the photographed image is converted into a monochrome image of 256 gradations using image analysis software. The value obtained by subtracting 30 from the most frequent brightness value in the monochrome image is used as a threshold value, and the brightness is binarized with values ​​less than the threshold value as black and values ​​equal to or greater than the threshold value as white. ２ The ratio of the total area of ​​black areas of the above size is defined as the black area ratio.

2. A resin substrate for a gas barrier film selected by the selection method according to claim 1.

3. The resin substrate for a gas barrier film according to claim 2 , wherein the resin substrate contains an antiblocking agent.

4. The resin substrate for a gas barrier film according to claim 2 or 3, wherein the resin substrate is one selected from the group consisting of polypropylene, polyethylene terephthalate, polyethylene, and nylon.

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